测试对Vector容器，遍历元素删除满足条件元素，而进行Erase()操作的效率

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#vector #测试 #iterator #include

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本文通过两个函数Erasefun和Otherfun对比了不同方式从C++标准库vector中删除小于特定数值的元素的效率。实验分别在100个元素及10万个元素的情况下进行，结果显示Otherfun在两种情况下都表现出更高的效率。

#include <Windows.h> #include <iostream> #include <vector> #include <cstdlib> using namespace std; void printVect(const vector<int> &v) { for(vector<int>::const_iterator it=v.begin(); it!=v.end(); ++it) { cout << *it << ','; } } void cheakVect(const vector<int> &v, const int cheakN) { for(vector<int>::const_iterator it=v.begin(); it!=v.end(); ++it) { if ((*it)<cheakN) { cout << "error!" << endl; break; } } } void Erasefun(vector<int> &v, const int N) { typedef vector<int>::iterator VI; for (VI it=v.begin(); it!=v.end(); ) { if ((*it) < N) { v.erase(it); it = v.begin(); continue; } it++; } } void Otherfun(vector<int> &v, const int N) { vector<int> tmp; typedef vector<int>::iterator VI; for (VI it=v.begin(); it!=v.end(); it++) { if ((*it) >= N) tmp.push_back(*it); } v.swap(tmp); } int main() { srand(::GetTickCount()); vector<int> v; int N = 50000; for (int i=0; i<2*N; ++i) { int r = rand()%(2*N); v.push_back(r); } //printVect(v); cout << "-----------------------------"<<endl; DWORD startTime1 = ::GetTickCount(); Erasefun(v, N); DWORD finTime1 = ::GetTickCount(); cout << "Erasefunc HT = "<< finTime1 - startTime1 << " ms" << endl; cheakVect(v, N); DWORD startTime2 = ::GetTickCount(); Otherfun(v,N); DWORD finTime2 = ::GetTickCount(); cout << "Otherfunc HT = "<< finTime2 - startTime2 << " ms" << endl; cheakVect(v, N); //printVect(v); return 0; }

100000个元素情况下：

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Erasefunc HT = 3734 ms

Otherfunc HT = 0 ms

100个元素情况：

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Erasefunc HT = 16 ms

Otherfunc HT = 0 ms