Codeforces 320A - Raising Bacteria(思维)

A. Raising Bacteria
time limit per test1 second
memory limit per test256 megabytes
inputstandard input
outputstandard output
You are a lover of bacteria. You want to raise some bacteria in a box.

Initially, the box is empty. Each morning, you can put any number of bacteria into the box. And each night, every bacterium in the box will split into two bacteria. You hope to see exactly x bacteria in the box at some moment.

What is the minimum number of bacteria you need to put into the box across those days?

Input
The only line containing one integer x (1 ≤ x ≤ 109).

Output
The only line containing one integer: the answer.

Examples
input
5
output
2
input
8
output
1
Note
For the first sample, we can add one bacterium in the box in the first day morning and at the third morning there will be 4 bacteria in the box. Now we put one more resulting 5 in the box. We added 2 bacteria in the process so the answer is 2.

For the second sample, we can put one in the first morning and in the 4-th morning there will be 8 in the box. So the answer is 1.

题意:
细菌每天会增加两倍,你每天都可以往培养皿里面放一定数量的细菌,问最少放几个,使得在某一天培养皿中的细菌数量恰好为N.

解题思路:
每天增加两倍,即二进制中向左移一位.所以只要在适当的时间节点上放一个,就可以满足.
即看所给数的二进制数中,有多少个1.

AC代码:

#include<stdio.h>
int main()
{
    int n;
    scanf("%d",&n);
    int cnt = 0;
    while(n)
    {
        if(n&1) cnt++;
        n >>= 1;
    }
    printf("%d",cnt);
    return 0;
}