计算小于或等于一个数字的正值之和

Question

I am trying to calculate the sum of positive values smaller or equal to the entered number, for ex: 5 -> 1+2+3+4+5 = 15

I came up with this:

 var num = Number(prompt("Enter a number ")); sum = 0; i = num; do { sum = sum += i; i-- document.write(sum); } while (i > 0); 

I don't understand what I am doing wrong.

Answer 1

i think this is correct code:

var num = Number(prompt("Enter a number "));
sum = 0;
i = num;
do 
{
  sum += i;
  i--;
}
while (i > 0);
document.write(sum);

and i suggest you to use this formula : document.write((num * (num + 1)) / 2);

Answer 2

If you look closer to your task, you'll find out, that:

If Num = 1, the sequence to be summed is [1]

if Num = 2, the sequence is [1, 2]

if Num = 3, the sequence is [1, 2, 3]

You can imagine, that you have a square with sides equal to num, for example, when num = 4:

****
****
****
****

And you need to summ 1, 2, 3, 4:

***#
**##
*###
####

See? It's a square of a triangle.

It could be calculated by formula: num * (num + 1) / 2

So, you code could be:

var num = Number(prompt("Enter a number "));
document.write(num * (num + 1) / 2)

Answer 3

You should write the answer at the end of loop and make this simple sum += i;.

 var num = Number(prompt("Enter a number")); sum = 0; i = num; do { sum += i; i--; } while (i > 0); document.write(sum); 

Answer 4

You are writing the sum on each loop instead you have to print it finally. If you want to print the numbers then keep it an array and join them with + symbol before writing. To make it in ascending order change the loop condition.

 var num = Number(prompt("Enter a number ")); sum = 0; i = 1; nums = []; do { sum = sum += i; nums.push(i++); } while (i <= num); document.write(nums.join(' + ') + ' = ' + sum); 

Answer 5

Do with increment instead of decrements.And also show result of sum outside of loop .Not with in loop.And create array to append increment value.Finally print with document.write

 var num=Number(prompt("Enter a number ")); sum = 0; i = 1; var a=[]; do { sum +=i; a.push(i) i++; } while (num >= i); document.write(a.join('+')+'='+sum) 

Answer 6

var number = 5, // Your number
    result = 0;

while ( number !== 0 ) {
    result += number;
    number--;
}

document.write(result);

Fast and precious solution.

Answer 7

Here is the case with complete check and display as you need: JAVA

     public static void main ( String arg[]) {

    Scanner scan = new Scanner(System.in);
    int number = scan.nextInt();
    System.out.println("Number entered :  " + number);
    int sum =1 ;

    if(number > 1) {

        int nextNumber = 1;
        System.out.print(nextNumber);

        do {
            // sum of all the positive numbers 
            nextNumber++ ;
            sum = nextNumber + sum;
            System.out.print( " + " + nextNumber);

        }while(nextNumber < number);

        System.out.print(" = " + sum);
    }
}

Answer 8

 var num = Number(prompt("Enter a number")); sum = 0; for (i = num; i > 0; i--) { sum += i; } document.write(sum);