C++语法部分补充

1、数字转字符串

C++ string与int互转

https://www.cnblogs.com/smile233/p/8379802.html

//字符串转数字
string str = "123";
int n = atoi(str.c_str());
str = "123.123";
float n = atof(str.c_str());
//数字转字符串
#include<string>
s=to_string(1.123)

C++输入输出

int tp;
while(cin>>tp){
    
}
int a[200];
while(cin>>x){
    a[++n]=x;
}
#include<iostream>
using namespace std;
int main(){
    int a,b;
    while(cin>>a>>b)
        cout<<a+b<<endl;
    return 0;
}
#读入一整行
string str; getline(cin,str);

int main()
{
    int n, m;
    vector<double> test;
    while (cin>>n>>m)//循环多行输入，回车换行，Ctrl+Z可结束循环
    {
        test.push_back(qiuhe(n, m));
    }
    for (int i = 0; i < test.size(); ++i)
    {
        cout << fixed << setprecision(2) << test[i] << endl;
    }
    return 0;
}

#include<iostream>
#include<string>
#include<cstdio>
using namespace std;
int main(){
string s;
getline(cin, s);
int n = atoi(s.c_str());
string now[n];

for (int i = 0; i < n; i++)
{
    getline(cin, now[i]);
}
for (int i = 0; i < n;i++){
    cout << now[i] << endl;
}
printf("%.2f", 0.21314);

return 0;
}

常见问题

https://blog.csdn.net/akenseren/article/details/80815799?utm_medium=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-1.vipsorttest&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-1.vipsorttest

1、输入vector

#include "stdlib.h"
#include <iostream>
#include<vector>
#include <iomanip>
using namespace std;
 
int main()
{
    int m, n;
    //cout << "请输入行和列：";
    cin >> m >> n;
 
    //注意下面这一行：vector <int后两个 "> "之间要有空格！否则会被认为是重载 "> > "。   
    vector<vector<int> > p(m, vector<int>(n));
 
    //cout << "请输入数据：";
    for (int i = 0; i < m; i++)
        for (int j = 0; j < n; j++)
            cin >> p[i][j];
 
    //cout << "输出数据：" << endl;
    for (int i = 0; i < m; i++)
    {
        for (int j = 0; j < n; j++)
            cout << setw(3) << p[i][j];
        cout << endl;
    }
    system("pause");
    return 0;
}

保留小数

printf("%.2f\n", test[i]);
//cout << fixed << setprecision(2) << test[i] << endl;

%f 对应 float
%lf 对应 double
%Lf 对应 long double
%e以科学计数法显示
%g在%e和%f中择短显示