笔试编程题输入输出模板备忘

C语言：

借用C中的malloc/free

#include "stdlib.h"


int main()
{
    int m, n;
    int i, j;
    int **p;

    scanf("%d%d", &m, &n); //请输入数组行和列

    p = (int**)malloc(sizeof(int*)*m); //开辟行  

    for (i = 0; i < m; i++)
    {
        *(p + i) = (int*)malloc(sizeof(int)*n);//开辟列  
    }
    //输入数据  
    for (i = 0; i < m; i++)
        for (j = 0; j < n; j++)
            scanf("%d", &p[i][j]);

    //输出数据  
    for (i = 0; i < m; i++)
    {
        for (j = 0; j < n; j++)
        {
            printf("%3d ", p[i][j]);
        }
        printf("\n");
    }
    //释放开辟的二维空间  
    for (i = 0; i < m; i++)
        free(*(p + i));
    system("pause");
    return 0;
}

C++：

借用C++中的new/delete

#include "stdlib.h"
#include <iostream>
using namespace std;


int main()
{
    int m, n;
    //cout << "请输入行和列：";
    cin >> m >> n;

    //动态开辟空间  
    int **p = new int*[m]; //开辟行  
    for (int i = 0; i < m; i++)
        p[i] = new int[n]; //开辟列  

    //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 << p[i][j];
        cout << endl;
    }

    //释放开辟的资源  
    for (int i = 0; i < m; i++)
        delete[] p[i];
    delete[] p;
    system("pause");
    return 0;
}

STL中的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;
}

多行输入，Ctrl+Z可退出

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;
}

Ctrl+Z在Windows下为文件结束符EOF（End of File）,Unix/Linux下为组合键Ctrl+D

scanf函数的原型是返回输入的个数：

int test2 = scanf("%d%d", &n, &m);//test2 =2

输出小数，保留两位精度

http://www.cplusplus.com/reference/iomanip/setprecision/

// setprecision example
#include <iostream>     // std::cout, std::fixed
#include <iomanip>      // std::setprecision
using namespace std;

int main () {
  double f =3.14159;
  cout << setprecision(5) << f << '\n'; //3.1416
  cout << setprecision(9) << f << '\n'; //3.14159
  cout << fixed;
  cout << setprecision(5) << f << '\n'; //3.14159
  cout << setprecision(9) << f << '\n'; //3.141590000
  return 0;
}

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

输出动态长度的数字，空格间隔，回车完成输入

#include <iostream>
#include <vector>
// #include <stdlib.h>
// #include <stdio.h>

using namespace std;

int main()
{
    vector<int> numbers;
    while (1)
    {
        int temp;
        cin >> temp;
        // scanf("%d", &temp);
        numbers.push_back(temp);
        char s = cin.get(); //s用来接收是否是回车
        // s = getchar(); //s用来接收是否是回车
        if (s == '\n')
        {
            break;
        }
    }

    for (int i = 0; i < numbers.size(); i++)
    {
        cout << numbers[i] << " ";
    }

    system("pause");
    return 0;
}