lower_bound & upper_bound
#include<bits/stdc++.h>
using namespace std;
int main(){
vector<int> v={1,2,3,4,5};
auto p = lower_bound(v.begin(),v.end(),3);
cout<<*p<<endl;
auto q = upper_bound(v.begin(),v.end(),3);
cout<<*q<<endl;
return 0;
}#include <iostream> // std::cout
#include <algorithm> // std::lower_bound
#include <vector> // std::vector
using namespace std;
//以普通函数的方式定义查找规则
bool mycomp(int i, int j) { return i > j; }
//以函数对象的形式定义查找规则
class mycomp2 {
public:
bool operator()(const int& i, const int& j) {
cout << "=== i: " << i << " === j: " << j << "\n" ;
return i > j;
}
};
int main() {
int a[5] = { 1,2,3,4,5 };
//从 a 数组中找到第一个不小于 3 的元素
int* p = lower_bound(a, a + 5, 3);
cout << "*p = " << *p << endl;
vector<int> myvector{ 4,5,3,1,2 };
//根据 mycomp2 规则，从 myvector 容器中找到第一个违背 mycomp2 规则的元素
vector<int>::iterator iter = lower_bound(myvector.begin(), myvector.end(), 3, mycomp2());
cout << "*iter = " << *iter;
return 0;
}#include <iostream> // std::cout
#include <algorithm> // std::upper_bound
#include <vector> // std::vector
using namespace std;
//以普通函数的方式定义查找规则
bool mycomp(int i, int j) { return i > j; }
//以函数对象的形式定义查找规则
class mycomp2 {
public:
bool operator()(const int& i, const int& j) {
cout << "=== i: " << i << " === j: " << j << "\n";
return i > j;
}
};
int main() {
int a[5] = { 1,2,3,4,5 };
//从 a 数组中找到第一个大于 3 的元素
int* p = upper_bound(a, a + 5, 3);
cout << "*p = " << *p << endl;
vector<int> myvector{ 4,5,3,1,2 };
//根据 mycomp2 规则，从 myvector 容器中找到第一个违背 mycomp2 规则的元素
vector<int>::iterator iter = upper_bound(myvector.begin(), myvector.end(), 3, mycomp2());
cout << "*iter = " << *iter;
return 0;
}