clock()

·clock()计时函数
  clock()是C/C++中的计时函数，而与其相关的数据类型是clock_t。在MSDN中，查得对clock函数定义如下：clock_t clock(void) ;简单而言，就是该程序从启动到函数调用占用CPU的时间。这个函数返回从“开启这个程序进程”到“程序中调用clock()函数”时之间的CPU时钟计时单元（clock tick）数。

·例子：

// ConsoleApplication1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include<ctime>
using namespace std;

struct ListNode {
	int m_nValue;
	ListNode *m_pNext;
};

// pHead指向第一个node
void AddToTail(ListNode * &pHead, const int &value) {
	ListNode* pNew = new ListNode();
	pNew->m_nValue = value;
	pNew->m_pNext = NULL;

	if (pHead == NULL) {
		pHead = pNew;
	}
	else {
		ListNode *pNode = pHead;
		while (pNode->m_pNext != NULL) {
			pNode = pNode->m_pNext;
		}

		pNode->m_pNext = pNew;
	}
}

void AddToTail2(ListNode **pHead, const int &value) {
	ListNode* pNew = new ListNode();
	pNew->m_nValue = value;
	pNew->m_pNext = NULL;

	if (*pHead == NULL) {
		*pHead = pNew;
	}
	else {
		ListNode *pNode = *pHead;
		while (pNode->m_pNext != NULL) {
			pNode = pNode->m_pNext;
		}

		pNode->m_pNext = pNew;
	}
}


//void RemoveNode(ListNode **pHead, int value)

int main()
{
	ListNode *pHead = NULL;
	ListNode *pHead2 = NULL; 
	clock_t startTime, endTime;

	startTime = clock();
	for (int i = 0; i < 10000*10; i++) {
		AddToTail(pHead, i);
	}
	endTime = clock();
	cout << endTime - startTime << endl;

	startTime = clock();
	for (int i = 0; i < 10000*10; i++) {
		AddToTail2(&pHead2, i);
	}
	endTime = clock();
	cout << (double)(endTime - startTime)/CLOCKS_PER_SEC << endl;

	/*
	while (pHead != NULL) {
		cout << pHead->m_nValue << endl;
		pHead = pHead->m_pNext;
	}

	while (pHead2 != NULL) {
		cout << pHead2->m_nValue << endl;
		pHead2 = pHead2->m_pNext;
	}*/
	
    return 0;
}