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What would be most efficient way to find number of 1 in a variables?

+1 vote
What would be most efficient way to find number of 1 in a variables?
posted Nov 3, 2014 by anonymous

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Didn't get you, can you please elaborate the question with sample input and your expected output.
Say the input is 00110011 then the output should be 4 as number of one's in the number is 4.

2 Answers

+1 vote

Use bit wise and operator (&) with 1 on you number. Do this on each bit of your number.
Here is my C program (Tested).

#include <stdio.h>

int num_ones_present(int num)
    int i = 0;

    while (num) {
        i += (num & 1);  //It will return 1 if num's 0th bit is 1 else return 0.
        num >>= 1;

    return i;

int main()
    int num, next_num, i = 0;
    int num_ones = 0;

    printf("Enter the number : ");
    scanf("%d", &num);

    num_ones = num_ones_present(num);
    printf("Then given number is : %d which has %d num of 1's\n", num, num_ones);

    return 0;

Happy Coding :)

answer Nov 5, 2014 by Arshad Khan
0 votes
int main()
   int count = 0,x;
   printf("Enter Number\n");
      x = x & x-1;
   printf("Number of on bits[%d]\n", count);
   return 0;
answer Nov 8, 2014 by Neeraj Mishra
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