Chapter 4 - Exercises

Javascript Programming
#62

SUM OF RANGE

<html>

    <head>
        <title>PART3</title>
        <h1>PART3param</h1>
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    </head>


    <body>
      <h2>SumRange</h2>
      <input type ="number" id="StartVal" value=0 title="Start value"/>
      <input type="number" id="EndVal" value=0 title="End value"/>
      <input type="number" id="Step" value=0 title="input step interval"/>
      <button id="Calc">Calculate</button>
      <br><br>
      <h4>ListNumbers:</h4><br>
      <ol id="ordList"></ol><br>
      <h4 id="SumNum">Sum of numbers:</h4><br>

      <script>


          //Create array of numbers
          function MakeArray(a,b,c) {
            var numbers = [];
            var numList = $("#ordList");
            var sumall = 0;


            numbers.length = 0;
            //check negative --> switch vars
            if ( Number(c) < 0 ) {
              //make array
              for (i=Number(b); i>=Number(a) ; i=i+Number(c)) {
                numbers.push(i);
                sumall += i;
                $("<li/>").text(i).appendTo(numList);
              }
      
            }
            else {
              //make array
              for (i=Number(a); i<=Number(b) ; i=i+Number(c)) {
                numbers.push(i);
                sumall += i;
                $("<li/>").text(i).appendTo(numList);
              }
            }
            $("#SumNum").text("Sum of all numbers in array= " +sumall);
            console.log(numbers)
          };

            //when button clicked
            $( "#Calc" ).click(function() {
                $("#ordList").html("");
                MakeArray( $('#StartVal').val(), $('#EndVal').val(), $('#Step').val() );
              });



      </script>

    </body>
</html>

Reversing array

<html>

    <head>
        <title>PART3</title>
        <h1>P3: ReverseArray</h1>
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    </head>


    <body>
      <h2>ReverseArray</h2>
      <input type ="number" id="StartVal" value=0 title="Start value"/>
      <input type="number" id="EndVal" value=0 title="End value"/>
      <input type="number" id="Step" value=0 title="input step interval"/>
      <button id="Calc">Process</button>
      <br><br>
      <h4>ListNumbers:</h4><br>
      <ol id="ordList"></ol><br>
      <h4>ListNumbers ReverseArray:</h4><br>
      <ol id="ordListRev"></ol><br>
      <h4>ListNumbers ReverseArrayInPlace:</h4><br>
      <ol id="ordListRevIp"></ol><br>

      <script>
          var numbers = [];
          var RevNumbers = [];

          function showarray(ar,name){
            //show an array that comes in: par1 is the array itsel, par2 is the name of the array
            $.each(ar, function( i, value ) {
              $("#"+name).append("<li>"+ value + "</li>");
            });
          };

          //Create array of numbers
          function MakeArray(a,b,c) {
            numbers.length = 0; // make sure array is empty
            //make numbers array based on parameters
            for (i=Number(a); i<=Number(b) ; i=i+Number(c)) {
                numbers.push(i);
              }
            showarray(numbers,"ordList");
          };

          //reverse an array that comes in and store it in another array
          function ReverseArray(a) {
              RevNumbers.length = 0; // make sure array is empty
              for (i=a.length; i > 0  ; i--) {
                  RevNumbers.push([i]);
                }
              showarray(RevNumbers,"ordListRev");
            };

            //reverse an array that comes in and store it in the same array
            function ReverseArrayInPlace(a) {
                //make temp array
                var temparray = [];
                temparray.length = 0; // make sure array is empty
                var b = 0;
                for (i=a.length-1; i >= 0  ; i--) {
                    temparray.push(a[i]);
                    b++;
                  }
                a.length = 0; //empty original array
                for (i=0; i < temparray.length  ; i++) {
                      a.push(temparray[i]);
                    }
              //  temparray.length = 0;
                showarray(a,"ordListRevIp");
              };


          //when button clicked
          $( "#Calc" ).click(function() {
                $("#ordList").html("");
                $("#ordListRev").html("");
                $("#ordListRevIp").html("");
                MakeArray( $('#StartVal').val(), $('#EndVal').val(), $('#Step').val() );
                ReverseArray(numbers);
                ReverseArrayInPlace(numbers);
              });



      </script>

    </body>
</html>

question about performance

Some things can more efficiently be expressed by using side effects, so that would be the reason not to go for a pure function because it can be slower
#63

The Sum of a Range:

function range(start, end, step)
{
    var array = [];
    if(typeof step != "undefined")
        if (step > 0){
            for(var i = start; i <= end; i+=step)
                array.push(i);
        
            return array;
        }
        else if(step < 0){
            for(var i = start; i >= end; i+=step)
                array.push(i);
        
            return array;
        }
        else{
            console.log("Step Error!");
            return 0;
        }
    else{
        for(var i = start; i <= end; i++)    
        array.push(i);
                       
        return array;
    }           
};

function sum (array)
{
    var cont = 0;

    for(var i = 0; i < array.length; i++){
        cont += array[i];
    }

    return cont;
}

var array1 = range(10,-1,-1);
console.log(array1);

var suma = sum(array1);
console.log(suma);

Result:
Array(12) [ 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, -1 ]
54

Reversing an Array:

function reverseArray(array)
{
    var newArray = [];
    var j = array.length-1;

    for(var i = 0; i < array.length; i++)
    {
        newArray[i] = array[j];
        j--;
        console.log(newArray);
    }
    
    return newArray;
};

function reverseArrayInPlace(array) // Book Solution
{
   for(var i = 0; i < Math.floor(array.length/2); i++){

        var temp = array[i];
        array[i] = array[array.length - 1 - i];
        array[array.length -1 - i] = temp;
        console.log(array);
   }
   return array;
};

var array = [1, 2, 3, 4, 5];
reverseArray(array);
console.log("----------------");
var array = [1, 2, 3, 4, 5];
reverseArrayInPlace(array);

Result:

Array [ 5 ]
Array [ 5, 4 ]
Array(3) [ 5, 4, 3 ]
Array(4) [ 5, 4, 3, 2 ]
Array(5) [ 5, 4, 3, 2, 1 ]
----------------
Array(5) [ 5, 2, 3, 4, 1 ]
Array(5) [ 5, 4, 3, 2, 1 ]

Discussion:

The second solution shows how with only two iterations we can have the problem solved. As well, the second solution does not include a new structure to the code only a simple variable. In my opinion, the reverseArrayInPlace function is better because it is a pure function, has no side effects, saves memory and it is faster.

#64

Hey. Here’s my code for exercise 4:

The sum of a range

function range(start, end, step=1) {
  rangeArray = [];
  if(step > 0) {
    for(var i = start; i <= end; i+=step) {
      rangeArray.push(i);
    }
  }
  else {
    for(var i = start; i >= end; i+=step) {
      rangeArray.push(i);
    }
  }
  return rangeArray;
}

function sum(range) {
 answer = 0;
  for(var i = 0; i <= range.length; i++) {
    answer += i;
  }
  return answer;
}

Reversing an array

function reverseArray(array) {
  reverse = [];
  for(let item of array) {
   reverse.unshift(item); 
  }
  return reverse;
}

I’m still working on the ‘reversing in place’, but for now, it’s back to work…

#65

had some trouble with bringing the array value out, it only works if the functions were wrapped around my range function.

#66
Sum of an Array 
function range (start, end, step = 1) {
  if (step === 0) {
    step++;
  }
  let list = [];
  if (step > 0) {
    while (start <= end) {
      list.push(start);
      start = start + step;
    }
    return list;
  }
  else {
    while (start >= end) {
      list.push(start);
      start = start + step;
    }
    return list;
  }
}

function sum (list) {
  let total = 0;
  for (let i = 0; i < list.length; i++) {
    total = total + list[i];
  }
  return total
}
Reversing an Array 
function reverseArray(list) {
  let rev = []
  for (let i = 1; i <= list.length; i++) {
    rev.push(list[list.length - i]);
  }
  return rev
}

function reverseArrayInPlace(list) {
  lon = list.length;
  for (let i = lon; i > 0; i--) {
    list.push(list[i-1]);
  }
  for (let i = 0; i < lon; i++) {
    list.shift();
  }
}
#67

Range() and Sum()

function range(start,end,step=1){
    result=[];
     if(start>end){
     //make start <= end
          temp=start;
          start=end;
          end=temp;
      }
     if(step==0){//if step is 0 then return empty result
          return result;
     }
     if(step<0){//for negative step go from end to start
          for(i=end;i>=start;i+=step){
               result.push(i);
           }
      }else{//for positive step go from start to end
          for(i=start;i<=end;i+=step){
               result.push(i);
           }
      }
     return result;
}

function sum(arr){
     result=0;
     for(let i in arr){
          result+=arr[i];
      }
      return result;
}

Reversing an array

reverseArray()

function reverseArray(arr){
     result=[];
     for(let i in arr){
          result.unshift(arr[i]);
     }
     return result;
}

reverseArrayInPlace()

  function rev(arr){
     		for(i=0;i<(arr.length/2);i++){

  		//swap only if i is not at middle
  		if(i!=arr.length/2&&i!=arr.length-(i+1)){
  
  			//swap in place
         	arr[i]=arr[i]+arr[arr.length-(i+1)];
          	arr[arr.length-(i+1)]=arr[i]-arr[arr.length-(i+1)];
  			arr[i]=arr[i]-arr[arr.length-(i+1)];
          }
      }
      return arr;
  }
#68

having a good deal of difficulty with this, but I think this is right…

The sum of a range:
function range(start, end) {
var rangeArray= [];
if(start < end) {
let index= 0;
for (let i= start; i<=end; i++){
rangeArray[index] = start+index;
}
} else {
alert(“Provide argument where start is smaller than the end.”);
}
console.log(rangeArray);
}
range(5,10);

Reversing an array: *this is one I had a lot of trouble with:

function reverseArray (int arr[], int start, int end){
while (start < end)
{
int temp = arr[start];
arr[start] = arr[end];
arr[end] = temp;
start ++;
end–;
} else {
function reverseArrayInPlace(start > end, start++);
}
void printArray(int arr[], int size)
{
for (int i = 0; i < size; i++)
cout << arr[i] << " ";

cout << endl;
}
}
int main()
{
int arr[] = {1, 2, 3, 4, 5, 6};

// To print original array
printArray(arr, 6);
 
// Function calling
rvereseArray(arr, 0, 5);
 
cout << "Reversed array is" << endl;
 
// To print the Reversed array
printArray(arr, 6);
 
return 0;

}
}

#69

//The Sum of a Range:
let arr = [];
let sumTotal = 0;

	function range (start, end, step) {

		if(step==undefined){
		for (i=start; i<=end; i++){
			arr.push(i);
		}
		return arr;
		}else if (step > 0){
			for(i=start; i<=end; i+=step){
				arr.push(i);
			}
			return arr;
		}else {
			for (i=start; i>=end; i+=step){
				arr.push(i);
			}
			return arr;
		}
	}


	function sum(myArray) {

		for(i=0 ; i< myArray.length; i++){
			sumTotal = sumTotal+myArray[i];
		}
		return sumTotal;

	}
#70

//reverse array
let myArray = [1,2,3,4,5,6,7,8,9,10];
let newArray =[];

	function reverseArray(arr) {
		for(i = arr.length -1; i >=0; i--) {
			newArray.push(arr[i]);
		}
		return newArray;
	}
#71

//reverse array in place
function reverseArrayInPlace(arr) {
let numOfSwaps = Math.floor(arr.length / 2);
for(i=0 ; i < numOfSwaps; i++) {
let holdValue = arr[i];
arr[i]=arr[arr.length-1-i];
arr[arr.length-1-i]=holdValue;
}
return arr;
}

#72 
  1.      <script>
   function range(a,b,c=1){
     let ran_array = [];
     if (a<b){
       for (let i=a; i<=b;i+=c){
         ran_array.push(i);
       }
       return ran_array;
     }
     else{
       if(c<0){
         for (let i=a; i>=b;i+=c){
           ran_array.push(i);
         }
         return ran_array;
       }
       else{
         return 'not possible'
       }
     }
   }
   function sum(numbers){
     let summ = 0;
     for(let numbs of numbers){
       summ += numbs;
     }
     return summ;
   }
   console.log(sum(range(1,10)));
   console.log(sum(range(1,10,2)));
   console.log(range(5,2,-1));
   </script>

  2.  <script>
     let first_array = ['q','w','e','r','t'];
     let second_array = ['q','w','e','r','t'];
     function reverseArray(a) {
       let new_array = [];
       for (let i of a){
         new_array.unshift(i);
       }
       return new_array;
     }
     function reverseArrayInPlace(a) {
       a_len = a.length;
       for(let i=0;i<=Math.floor(a_len/2);i++){
         let old_val = a[i];
         console.log(old_val);
         a[i] = a[a_len-1-i];
         a[a_len-i-1] = old_val;
       }
       return a;
     }
     console.log(reverseArray(first_array));
     console.log(first_array);
     console.log(second_array);
     console.log(reverseArrayInPlace(second_array));
     console.log(second_array);
   </script>
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#73

Actually var (or let) is no needed in code until is really needed:) Code works even when you take out all var-s (or let-s):P:)

1 Like
#74

**Chapter 4 **

EX 1
The sum of a range

      function ArRange(x,y,step){
      arr=[];
      for (counter=x; counter<=y; counter+=step){
        arr.push(counter);
        }
      console.log(arr);
    }

    function ArSum(arr){
    var sum=0;
    var n=arr[arr.length-1];
    $.each(arr, function(index, value){
         sum +=value;
     });
       console.log(sum);
     }
           ArRange(1,10,1);
           ArSum(arr);

EX2
Reverse Array

   function reverseArray(arr){
   var revArr=[];
   var n=arr.length-1;
    for (counter=n; counter>=0; counter--){
                  revArr.push(arr[counter]);
                   }
                   console.log(revArr);
                }


    function reverseArrayInPlace(arr){
              var arrLen=arr.length;
              for (counter=0; counter<(arrLen-1); counter++){
                    var old_val=arr[counter];
                    arr[counter]=arr[arrLen-1-counter];
                    arr[arrLen-1-counter]=old_val;
                }
                console.log(arr);
        }
1 Like
#75 
// The Sum of a Range
function range(start, end, step){
	let arrayRange = [];
  if(step){
    if(end < start){
      for(let i = start; i >= end; i+=step){
      	arrayRange.push(i)
      }
    }
    else {
      for(let i = start; i <= end; i+=step){
      	arrayRange.push(i)
      }
    }
  }
  else {
   for(let i = start; i <= end; i++){
      arrayRange.push(i)
    }
  }
  return arrayRange;
}

function sum(arraySum){
  let result = 0;
  for(let number of arraySum){
    result += number;
  }
  return result;
}


// Reversing an Array
console.log("Reversing an Array");
function reverseArray(a){
	let arrayNew = [];
	for(let i = a.length - 1; i >= 0; i--){
		arrayNew.push(a[i]);
	}
	return arrayNew;
}

function reverseArrayInPlace(a){
  for(let i = 0; i < Math.floor(a.length/2); i++){
		let aux = a[i];
		a[i] = a[a.length - 1 - i];
		a[a.length - 1 - i] = aux;
	}
	return a;
}
1 Like
#77

And that is my solution:

var sumValue = 0;

function sum(a){
  $.each(a,function(index,value){
    sumValue = value + sumValue;
    console.log(index, value, sumValue)
  });
  sumValue = 0;
}

function range (start,end,step){
  var array = [];
  if (step==0) {step = 1};
  if (start<end){
    for (start; start <= end; start = start + step){
      array.push(start);
    }
  }else if(start>end){
    for (start; start >= end; start = start + step){
      array.push(start);
    }
  }
  return array;
}
console.log(sum(range(1,10,2)));

function reverseArray(array){
  var newArray = [];
  for(var x = 0; x<array.length; x++){
    newArray.push(array[array.length-1-x]);
  }
  return newArray;
}
console.log(reverseArray([2,4,6]));

function reverseArrayInPlace(array){
  for(var x = 0; x<array.length;x++){
    var store1 = array[array.length-1-x];
    var store2 = array[x]
      console.log(store1,store2)
    array[x] = store1;
    array[array.length-1-x] = store2;
  }
  return array;
}
console.log(reverseArrayInPlace([2,4,6]));
1 Like
#78

The sum of a range

function range(start, end, step) {
var numbers = [];
if(step === undefined)
step = 1;
if(step>0)
for(var count=start; count<=end; count+=step) {
numbers.push(count);
} else
for(var count=end; count>=start; count+=step) {
numbers.push(count);
}
return numbers;
}

function sum(array) {
if(array.length === 0)
return 0;
return array.pop() + sum(array);
}

console.log(sum(range(1,10,1)));

1 Like
#79

Reversing an Array
function reverseArray(a){
let arrayNew = [];
for(let i = a.length - 1; i >= 0; i–){
arrayNew.push(a[i]);
}
return arrayNew;
}
console.log(reverseArray([2,4,6,10]));

function reverseArrayInPlace(a){
for(let i = 0; i < Math.floor(a.length/2); i++){
let aux = a[i];
a[i] = a[a.length - 1 - i];
a[a.length - 1 - i] = aux;
}
return a;
}
console.log(reverseArrayInPlace([2,4,6]));

1 Like
#80

Range Function

function range(start, end, step){
let arrayRange = [];
for(let i = start; i <= end; i++){
arrayRange.push(i)
};
return arrayRange;
};

Sum Function

function sum(a){
let result = 0;
for(let number of a){
result += number;
};
return result;
};

Reverse Array Function

function reverseArray(…a){
let arrayNew = [];
for(let i = a.length - 1; i >= 0; i–){
arrayNew.push(a[i]);
};
return arrayNew;
};

Reverse Array in Place Function

function reverseInPlace(…a){
let arr=[];
arr.push(…a);
for (var i = 0, j = arr.length - 1; i < j; i++, j–) {
var temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
};
return arr;
};

1 Like
#81

This is my solution to “The Sum of a Range”:

        function range(start, end, step) {

            let rangeArray = [];

            if(step == null || step == 1) {
                for(let i = start; i <= end; i++) {
                    rangeArray.push(i);
                }
            }else if(step < 0) {
                for(let i = start; i >= end; i+=step) {
                    rangeArray.push(i);
                }
            }else {
                for(let i = start; i <= end; i+=step) {
                    rangeArray.push(i);
                }
            }

            return rangeArray;
        }

        function sum(numberArray) {
            let totalSum = 0;
            for(let i = 0; i < numberArray.length; i++) {
                totalSum += numberArray[i];
            }
            return totalSum;
        }

        console.log(range(1, 10, 2));
        // Array(5) [ 5, 4, 3, 2, 1 ]

        console.log(sum(range(1, 10, 2)));
        // 15

“Reversing an Array”:

        let testArray = [0, 4, 10, 30, 49];

        function reverseArray(array) {
            let newArray = [];
            for(let i = array.length-1; i >=0; i--) {
                newArray.push(array[i]);
            }
            return newArray;
        }

        function reverseArrayInPlace(array) {
            for(let i = 0; i < Math.floor(array.length/2); i++) {
                let savedData = array[i];
                array[i] = array[array.length - 1 - i];
                array[array.length - 1 - i] = savedData;

            }
            return array;
        }

        console.log(reverseArray(testArray));
        //Array(5) [ 49, 30, 10, 4, 0 ]
        console.log(reverseArrayInPlace(testArray));
        //Array(5) [ 49, 30, 10, 4, 0 ]
#82

// Compute range between two parameters //
function computeRagme(start,end){
let arrayofNum = [];
let count = 0;
for(i = start; i <= end; i++){
arrayofNum[count] = i;
count++;
};
return(arrayofNum);
};

// Sum of a range //
function arraySum(arrayofNum){
let sum = 0;
for(let item of arrayofNum){
sum = item + sum;
};
return sum;
};

// Compute range between two pararameters allowing negative and positive steps //
function computeRange(start,end,step=1){
let arrayofNum = [];
let count = 0;
if(start < end){
for(i = start; i <= end; i=i+step){
arrayofNum[count] = i;
count++;
};
}else{
for(i = start; i >= end; i=i+step){
arrayofNum[count] = i;
count++;
};
};
return(arrayofNum);
};

// Reverse Array Creates New Arra //

function reverseArray(myArray){
arrayLength = myArray.length;
newArray = [];
for(let i=0; i < myArray.length; i++){
newArray[arrayLength-1] = myArray[i];
arrayLength = arrayLength - 1;
};
return newArray;
};

1 Like