第四十八节 C++ STL 算法

STL算法：

1 头文件 #include <algorithm>

2 算法通常与迭代器和函数对象一起使用

仅举几个例子。

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

/*1 函数模板：为了打印不同类型的内容*/
template <typename T1>
void DisplayContent(const T1 input) {
	int index = 0;

	cout << "  data: ";
	for (auto Iterator = input.begin(); Iterator != input.end(); ++Iterator) {
		index = std::distance(input.begin(), Iterator);
		cout << " " << *Iterator;
	}
	cout << endl;
}


int main()
{

	/*1 find(), find_if()*/
	cout << "1 find(), find_if() : " << endl;
	std::vector <int> intVector;
	for (int index = 0; index < 4; ++index) {
		intVector.push_back(index+4);
		intVector.push_back(index + 4);
	}
	DisplayContent(intVector);
	auto iElement = find(intVector.begin(), intVector.end(), 6); //使用find()查找第一个指定值6
	if (iElement != intVector.end()) {
		cout << "  find the value = " << *iElement << endl;
	}

	auto lambdaFormat1 = [] (const int& value) {
		return (value % 2 == 0);
	};

	auto iElement2 = find_if(intVector.begin(), intVector.end(), lambdaFormat1); //使用find_if()查找第一个满足lambdaFormat1条件的值
	if (iElement2 != intVector.end()) {
		cout << "  find_if the value = " << *iElement2 << endl;
	}

	/*2 count(), count_if()*/
	cout << "2 count(), count_if() : " << endl;

	int num  = count(intVector.begin(), intVector.end(), 6); //使用count()查找6的个数
	cout << "  the num1 = " << num << endl;

	int num2 = count_if(intVector.begin(), intVector.end(), lambdaFormat1); //使用count_if()查找满足条件的个数
	cout << "  the num2 = " << num2 << endl;

	return 0;
}

1 find(), find_if() :
  data:  4 4 5 5 6 6 7 7
  find the value = 6
  find_if the value = 4
2 count(), count_if() :
  the num1 = 2
  the num2 = 4