c++学习――容器搜索方法（lower_bound, uper_bound） - c++编程基础

本文主要是验证，容器搜索算法的使用：lower_bound, uper_bound
验证项目：
1. 当 key > begin 时 lower_bound, uper_bound 取值
2. 当 key < end 时 lower_bound, uper_boudn 取值
3. 当 key = 容器中的某值（不等于bigin，也不等于end）时 lower_bound, uper_boudn 取值
4. 当 key 在不等于容器中任何一Key，但是在key 的返回 ower_bound, uper_boudn 取值
5. 当 key 等于 bigin，当 key 等于 end 时的取值
测试代码：
[cpp]
#include "stdafx.h"
#include
#include

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
//lower_bound函数用法，这个函数用来返回要查找关键字的下界
//upper_bound函数用法，这个函数用来返回要查找关键字的上界
mapmp;

mp[3]="3";
mp[4]="4";
mp[7]="7";
mp[8]="8";

map::iterator iterLowerBound5,iterUperBound5;
map::iterator iterLowerBound7,iterUperBound7;
map::iterator iterLowerBound3,iterUperBound3;
map::iterator iterLowerBound8,iterUperBound8;
map::iterator iterLowerBound10,iterUperBound10;
map::iterator iterLowerBound1,iterUperBound1;

iterLowerBound5 = mp.lower_bound(5);
iterUperBound5 = mp.upper_bound(5);

iterLowerBound7 = mp.lower_bound(7);
iterUperBound7 = mp.upper_bound(7);

iterLowerBound3 = mp.lower_bound(0);
iterUperBound3 = mp.upper_bound(0);

iterLowerBound8 = mp.lower_bound(8);
iterUperBound8 = mp.upper_bound(8);

iterLowerBound10 = mp.lower_bound(10);
iterUperBound10 = mp.upper_bound(10);
if(iterLowerBound10 == mp.end())
cout << "iterUperBound10 = end" << endl;
if(iterUperBound10 == mp.end())
cout << "iterUperBound10 = end" << endl;

iterLowerBound1 = mp.lower_bound(1);
iterUperBound1 = mp.upper_bound(1);
if(iterLowerBound1 == mp.end())
cout << "iterUperBound1 = end" << endl;
if(iterUperBound1 == mp.end())
cout << "iterUperBound1 = end" << endl;

if(iterLowerBound1 == mp.begin())
cout << "iterUperBound1 = begin" << endl;
if(iterUperBound1 == mp.begin())
cout << "iterUperBound1 = begin" << endl;

//iter2 = mp.upper_bound(5);

string Str = iterLowerBound5->second;
cout<<"lower_bound(5) = " < Str = iterUperBound5->second;
cout<<"upper_bound(5) = " <
Str = iterLowerBound7->second;
cout<<"lower_bound(7) = " << Str.c_str()< Str = iterUperBound7->second;
cout<<"upper_bound(7) = " << Str.c_str()<
Str = iterLowerBound3->second;
cout<<"lower_bound(0) = " << Str.c_str()< Str = iterUperBound3->second;
cout<<"upper_bound(0) = " << Str.c_str()<
Str = iterLowerBound8->second;
cout<<"lower_bound(8) = " << Str.c_str()< //Str = iterUperBound8->second;
if(iterUperBound8 == mp.end())
cout<<"upper_bound(8) == end" << Str.c_str()<
while(1);
return 0;
}

打印输出：
iterLowerBound10 = end

iterUperBound10 = end

iterLowerBound1 = begin

iterUperBound1 = begin

lower_bound(5) = 7

lower_bound(7) = 7

lower_bound(7) = 8

lower_bound(0) = 3

lower_bound(8) = 8

lower_bound(8) = end8
结论：
当参数 key 没有在容器 key的范围内：
1. 小于容器key uper_bound， lower_bound 都将返回 begin.
2. 大于容器key uper_bound, lower_bound 都将返回 end
当参数key 在容器key 范围内：
1. 参数 key == 容器key. lower_bound 将返回当前key 的iterator， uper_bound 将返回下一个元素的iterator.
2. 参数 key 不等于容器key，且在范围内， loer_bound将返回比参数key 大的且相邻的容器key的iterator
3 如果 Key等于 begin 或等于 end，将返回begin 或end

摘自 DriverMonkey的专栏