《Cracking the Coding Interview》——第5章：位操作——题目1

2014-03-19 05:45

题目：给定两个数M和N，将N按照二进制位，覆盖到M的特定段位中去。

解法：位操作，请看代码。

代码：

// 5.1 Insert one number into the certain bit segment of another number.
#include <cstdio>
using namespace std;

void printBinary(unsigned num)
{
    unsigned bit = 1 << 31;
    
    do {
        putchar('0' + !!(num & bit));
        bit >>= 1;
    } while (bit);
}

unsigned insertBits(unsigned n, unsigned m, int ll, int rr)
{
    return (n >> (rr + 1) << (rr + 1)) + (m << ll) + (n - (n >> ll << ll));
}

int main()
{
    unsigned n, m;
    unsigned res;
    int low, high;
    
    while (scanf("%u%u", &n, &m) == 2) {
        scanf("%d%d", &low, &high);
        res = insertBits(n, m, low, high);
        printBinary(n);
        putchar('\n');
        printBinary(m);
        putchar('\n');
        printBinary(res);
        putchar('\n');
    }
    
    return 0;
}