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C++小细节笔记

article 2025/3/1 7:23:09

1、C++字符串转数字 – 数字转字符串

	//string => int   使用 stoi stol
	//int => string   使用 to_string()

2、C++遍历

	int evalRPN(vector<string>& tokens) {
        stack<int> intStack;

        for(string &str:tokens)
        {}

	bool isValid(string s) {
        stack<char> cs;
        for(char ch:s)
        {}

	int arr[10];
	
	for (int v : arr)
	{
		cout << v << "  ";
	}

3、生成随机数

#include<iostream>
#include<stdlib.h> //包含随机数函数srand
#include<time.h> //需要用time作为随机数种子

using namespace std;



int main()
{
	int arr[10];
	srand(time(NULL));
	
	for (int i = 0; i < 10; i++)
	{
		arr[i] = rand() % 100 + 1;
	}

	for (int v : arr)
	{
		cout << v << "  ";
	}
	cout << endl;

	return 0;
}

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4、查函数

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5、测试排序算法花费时间

int main()
{
	const int COUNT = 10000;
	int* arr = new int[COUNT];
	int* brr = new int[COUNT];
	int* crr = new int[COUNT];
	int* drr = new int[COUNT];

	srand(time(NULL));

	for (int i = 0; i < COUNT; i++)
	{
		int val = rand() % COUNT;
		arr[i] = val;
		brr[i] = val;
		crr[i] = val;
		drr[i] = val;
	}

	clock_t begin,end;

	begin = clock();
	BubbleSort(arr, COUNT);
	end = clock();
	cout << "BubbleSort spend: " << (end - begin) * 1.0 / CLOCKS_PER_SEC << "s" << endl;

	begin = clock();
	ChoiceSort(brr, COUNT);
	end = clock();
	cout << "ChoiceSort spend: " << (end - begin) * 1.0 / CLOCKS_PER_SEC << "s" << endl;

	begin = clock();
	InsertSort(crr, COUNT);
	end = clock();
	cout << "InsertSort spend: " << (end - begin) * 1.0 / CLOCKS_PER_SEC << "s" << endl;

	begin = clock();
	ShellSort(drr, COUNT);
	end = clock();
	cout << "ShellSort spend: " << (end - begin) * 1.0 / CLOCKS_PER_SEC << "s" << endl;

}