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c++学习——容器搜索方法(lower_bound, uper_bound)

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 <map> 
#include <iostream> 
 
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 
    map<int,string>mp; 
 
    mp[3]="3"; 
    mp[4]="4"; 
    mp[7]="7"; 
    mp[8]="8"; 
 
    map<int,string>::iterator iterLowerBound5,iterUperBound5; 
    map<int,string>::iterator iterLowerBound7,iterUperBound7; 
    map<int,string>::iterator iterLowerBound3,iterUperBound3; 
    map<int,string>::iterator iterLowerBound8,iterUperBound8; 
    map<int,string>::iterator iterLowerBound10,iterUperBound10; 
    map<int,string>::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.c_str()<<endl; 
    Str = iterUperBound5->second; 
    cout<<"upper_bound(5) = " <<Str.c_str()<<endl; 
 
    Str = iterLowerBound7->second; 
    cout<<"lower_bound(7) = " << Str.c_str()<<endl; 
    Str = iterUperBound7->second; 
    cout<<"upper_bound(7) = " << Str.c_str()<<endl; 
 
    Str = iterLowerBound3->second; 
    cout<<"lower_bound(0) = " << Str.c_str()<<endl; 
    Str = iterUperBound3->second; 
    cout<<"upper_bound(0) = " << Str.c_str()<<endl; 
 
    Str = iterLowerBound8->second; 
    cout<<"lower_bound(8) = " << Str.c_str()<<endl; 
    //Str = iterUperBound8->second; 
    if(iterUperBound8 == mp.end()) 
     cout<<"upper_bound(8) == end" << Str.c_str()<<endl; 
      
    while(1); 
    return 0; 

打印输出:
iterLowerBound10 = end

iterUperBound10 = end

iterLowerBound1 = begin

iterUperBound1 = begin

lower_bound(5) = 7

lower_bound(5) = 7

lower_bound(7) = 7

lower_bound(7) = 8

lower_bound(0) = 3

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

补充:软件开发 , C++ ,
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