swap：临时变量vs和交换vs位运算 时间对比

/*1 编写一个函数，不用临时变量，直接交换两个数*/void swap0(int* a, int* b){int temp;temp = *a;*a = *b;*b = temp;}void swap1(int* a, int* b){*a = *a + *b;*b = *a - *b;*a = *a - *b;}void swap2(int *a, int* b){*a = *a ^ *b;*b = *a ^ *b;*a = *a ^ *b;}#include "time.h"#include "iostream"int main(){clock_t t0;clock_t t1;int a = 1; int b = 2;t0 = clock();for (int i = 0; i < 10000; i++){for (int j = 0; j < 100; j++)swap0(&a, &b);}t1 = clock();std::cout << "swap0(): " << t1 - t0 << "ms" << std::endl;t0 = clock();for (int i = 0; i < 10000; i++){for (int j = 0; j < 100; j++)swap1(&a, &b);}t1 = clock();std::cout << "swap1(): " << t1 - t0 << "ms" << std::endl;t0 = clock();for (int i = 0; i < 10000; i++){for (int j = 0; j < 100; j++)swap2(&a, &b);}t1 = clock();std::cout << "swap2(): " << t1 - t0 << "ms" << std::endl;return 0;}

实验结果：

swap0(): 30msswap1(): 34msswap2(): 27ms

实验标明：速度 位运算>临时变量>和运算。

分析：和运算里用到了加减操作，所以会比临时变量慢。