Problem statement: Write a C program to count number of bits set to 1 in an Integer.

问题陈述：编写一个C程序来计算Integer中设置为1的位数 。

Solution: We can use bitwise operator here to solve the problem.

解决方案：我们可以在这里使用按位运算符来解决问题。

Pre-requisite: Input number n

前提条件 ：输入数字n

Algorithm:

算法：

1)  Set count=1
2)  Do bit wise AND with n and 1.
n & 1
let n be a7a6a5a4a3a2a1a0
1->00000001
So doing bitwise AND (refer to published article on bitwise operators)
will result in all bits 0 except the LSB which will be a0.
If a0 is 0 then the all bits are not set
Thus,
IF
n& 1 == 1
count++;
END IF
Right shift n by 1
n=n>>1
3)  IF n==0
Print count
ELSE
REPEAT step 1, 2

Example with Explanation:

解释示例：

Checking for 7
7->00000111
Initially, count=0
So first iteration:
n=7 //00000111
n & 1 =1
so , count=1
n=n>>1 (n=3) //00000011
So second iteration:
n=3 //00000011
n & 1 =1
count=2
n=n>>1 (n=1) //00000001
So third iteration:
n=1 //00000001
n & 1 =1
count=3
n=n>>1 (n=0) //00000000
So, Print count, 3

C implementation

C实现

#include <stdio.h>
int main()
{unsigned int n;
printf("enter the integer\n");
scanf("%d",&n);
int count=0;
while(n!=0){if(n & 1 == 1){ //if current bit 1
count++;//increase count
}
n=n>>1;//right shift
}
printf("no of bits those are 1 ");
printf("in its binary representation: %d\n",count);
return 0;
}

Output

输出量

First run:
enter the integer
7
no of bits those are 1 in its binary representation: 3
Second run:
enter the integer
12
no of bits those are 1 in its binary representation: 2

翻译自: https://www.includehelp.com/c-programs/count-number-of-bits-set-to-1-in-an-integer.aspx