STL查找相关算法

最新推荐文章于 2022-03-24 19:45:11 发布

原创最新推荐文章于 2022-03-24 19:45:11 发布 · 145 阅读

CC 4.0 BY-SA版权

本文介绍了C++标准库中几种常用的查找算法，包括adjacent_find用于查找相邻重复元素，binary_search针对有序数组进行快速查找，count计算指定元素出现次数，count_if与find_if则通过条件函数实现更灵活的搜索。

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#include<iostream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<functional>
#include<algorithm>


using namespace std;

// 查找相关算法
void main_44_adjecent_find()
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(3);
	v1.push_back(1);
	v1.push_back(5);

	//查找相邻的重复元素，返回重复元素的值
	vector<int>::iterator it = adjacent_find(v1.begin(), v1.end());
	if (it == v1.end())
	{
		cout << " 没有找到 重复元素" << endl;
	}
	else
	{
		cout << *it << endl;
	}
	int index = distance(v1.begin(),it);
	cout << index << endl;
}

void main_45_binary_search()//查找对象必须是有序的
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(5);
	v1.push_back(7);
	v1.push_back(9);

	//查找值为5的元素，返回bool值
	bool b = binary_search(v1.begin(), v1.end(), 5);
	if (b == true)
	{
		cout << "找到了！" << endl;
	}
	else
	{
		cout << "没找到！" << endl;
	}
}

void main_46_count()
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(5);
	v1.push_back(7);
	v1.push_back(9);

	//查找计算值为5的元素数量
	int num = count(v1.begin(), v1.end(), 5);
	cout << num << endl;
}

bool GreatThree(int &num)
{
	return num > 3;
}
void main_47_count_if()
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(5);
	v1.push_back(7);
	v1.push_back(9);

	//查找符合条件的元素数量
	int num = count_if(v1.begin(), v1.end(), GreatThree);
	cout << num << endl;
}

void main_47_find()
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(5);
	v1.push_back(7);
	v1.push_back(9);

	vector<int>::iterator it = find(v1.begin(), v1.end(), 5);
	cout << *it << endl;
}

void main_47_find_if()
{
	vector<int> v1;
	v1.push_back(1);
	v1.push_back(3);
	v1.push_back(5);
	v1.push_back(7);
	v1.push_back(9);

	//查找第一个大于3的元素
	vector<int>::iterator it = find_if(v1.begin(), v1.end(), GreatThree);
	cout << *it << endl;
}

void main()
{
	main_44_adjecent_find();
}