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(): 30ms
swap1(): 34ms
swap2(): 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。