{ans + = n << count”是什么意思？

Question

// Function for multiplication 
int multiply(int n, int m) 
{   
    int ans = 0, count = 0; 
    while (m) 
    { 
        if (m % 2 == 1)               
            ans += n << count; 

        // increment of place value (count) 
        count++; 
        m /= 2; 
    } 
    return ans; 
} 

该表达是什么意思？如何以更适合初学者的形式重写此表达式？

Answer 1

表达式ans += n << count;的含义与以下内容相同：

int n_shifted = n << count;  /* bitshift n to the left by count bits */
ans = ans + n_shifted;       /* add n_shifted to ans */

Answer 2

将n左移count，然后将其添加到ans

n << 1  =   n * 2
n << 2  =   n * 4
n << 3  =   n * 8
n << 4  =   n * 16

等