用加法模拟乘法

    /* 

         用加法模拟乘法 

     */  

      

    #include <stdio.h>  

    #include <stdlib.h>  

    //#define T(O,R,N,i) (N&(1<<i)) && (O+=(R<<i))  

    #define T(o,a,b,i) (b&1<<i) && (o+=a<<i)  

    int simulateMutiply(int a,int b)  

    {  

        int out=0;  

        T(out, a, b, 0);  

        T(out, a, b, 1);  

        T(out, a, b, 2);  

        T(out, a, b, 3);  

        T(out, a, b, 4);  

        T(out, a, b, 5);  

        T(out, a, b, 6);  

        T(out, a, b, 7);  

        T(out, a, b, 8);  

        T(out, a, b, 9);  

        T(out, a, b, 10);  

        T(out, a, b, 11);  

        T(out, a, b, 12);  

        T(out, a, b, 13);  

        T(out, a, b, 14);  

        T(out, a, b, 15);  

        T(out, a, b, 16);  

        T(out, a, b, 17);  

        T(out, a, b, 18);  

        T(out, a, b, 19);  

        T(out, a, b, 20);  

        T(out, a, b, 21);  

        T(out, a, b, 22);  

        T(out, a, b, 23);  

        T(out, a, b, 24);  

        T(out, a, b, 25);  

        T(out, a, b, 26);  

        T(out, a, b, 27);  

        T(out, a, b, 28);  

        T(out, a, b, 29);  

        T(out, a, b, 30);  

        T(out, a, b, 31);  

        return out;  

      

    }  

    int main(void) {  

        printf("%d \n",simulateMutiply(26,3));  

        return EXIT_SUCCESS;  

    }  

转自：http://blog.csdn.net/shandianling/article/details/8785481