The beauty of programming 1 -- the number of 1 in the binary representation of a number, the beauty of Binary

The beauty of programming 1 -- the number of 1 in the binary representation of a number, the beauty of Binary

Three solutions are introduced here.

First; (conventional solution)

The number is represented in binary in the computer, so the number n can be used consecutively to divide 2

Code 1:

<Span style = "font-size: 14px;" >#include <iostream> using namespace std; int main (void) {int n, m; m = 0; cin> n; while (n) {if (n % 2) // if n cannot divide 2, the end of the current n is 1 m ++; n >>= 1; // n shifts 1 to the right, that is, n/2} cout <m <endl; return 0 ;}</span>

Second: bitwise operations

&: If a is 1 and B is 1, a & B is 1. Otherwise, a & B is 0.

Here I = 0x1 is initialized;

If n & I is 1, the end of n is 1; otherwise, it is 0.

Code 2:

<Span style = "font-size: 14px;" >#include <iostream> using namespace std; int main (void) {// bit operation, 1. the last bit of the binary is used to calculate the int n, I, m; m = 0; I = 0x1; cin> n; while (n) {m + = (n & I); n >>= 1 ;}cout <m <endl; return 0 ;}</span>

Third: use another bit operation

If the binary value of n is 0010 0000, the second algorithm needs to be improved.

Allows n and n-1 to perform the & operation. If n & (n-1) = 0, it is the above case (only one of n's binary representation is 0 ).

Code 3:

<span style="font-size:14px;">#include <iostream>using namespace std;int main(void){      int n,m;    m=0;    cin>>n;    while(n)    {        n&=(n-1);        m++;    }    cout << m <<endl;     return 0;}</span>