C++基础：二维数组动态的申请内存和释放内存

使用二维数组的时候，有时候事先并不知道数组的大小，因此就需要动态的申请内存。常见的申请内存的方法有两种：malloc/free 和 new/delete。

一、malloc/free

（1）申请一维数组

void dynamicCreate1Array()
{
    int m;
    int i;
    int *p;
 
    cout<<("please input the length of data:");
    cin >> m;
 
    p = (int*)malloc(sizeof(int)*m);//动态开辟  
 
    cout << "please input data" << endl;
    for (i = ; i < m; i++)
        cin >> p[i];
 
    cout << "data is :";
    for (i = ; i < m; i++)
        cout << p[i] << endl;
    free(p);
}

（2）申请二维数组

void dynamicCreate2Array()
{
    int m, n;
    int i, j;
    int **p;
 
    printf("please input the row and col：");
    cin >> m >> n;
    //scanf("%d%d", &m, &n);
 
    p = (int**)malloc(sizeof(int*)*m); //开辟行  
 
    for (i = ; i < m; i++)
    {
        *(p + i) = (int*)malloc(sizeof(int)*n);//开辟列
    }
    //输入数据
    printf("please input data：");
    for (i = ; i < m; i++)
        for (j = ; j < n; j++)
            cin >> p[i][j];
    //输出数据
    for (i = ; i < m; i++)
    {
        for (j = ; j < n; j++)
        {
            cout << p[i][j];
        }
        cout << endl;
    }
    //释放开辟的二维空间
    for (i = ; i < m; i++)
        free(*(p + i));
}

二、new/delete

（1）申请一维数组

void DynamicCreate1Array()
{
    int len;
    int i;
 
    cout << "please input the length of data: ";
    cin >> len;
 
    int *p = new int[len];
 
    cout << "please input data: ";
    for (int i = ; i < len; i++)
        cin >> p[i];
 
    cout << "data is " << endl;
    for (i = ; i < len; i++)
        cout <<p[i] << endl;
 
    delete[] p;
}

（2）申请二维数组

void DynamicCreate2Array()
{
    int m, n;
    int i;
    cout << "input row and col: ";
    cin >> m >> n;
 
    //动态开辟空间
    int **p = new int*[m]; //开辟行
    for (int i = ; i < m; i++)
        p[i] = new int[n]; //开辟列  
 
    cout << "input data: ";
    for (i = ; i < m; i++)
        for (int j = ; j < n; j++)
            cin >> p[i][j];
 
    cout << "output: " << endl;
    for (i = ; i < m; i++)
    {
        for (int j = ; j < n; j++)
            cout <<  p[i][j]<<" ";
        cout << endl;
    }
 
    //释放开辟的资源
    for (i = ; i < m; i++)
        delete[] p[i];
    delete[] p;
 
}

注：另一种方法：

row：行

col：列

unsigned int **ppPathes;

*ppPathes = (unsigned int *)calloc(row * col, sizeof(unsigned int));

使用malloc：

*ppPathes = (unsigned int *)malloc(sizeof(unsigned int )*(PathNumTemp) * (pathLenTemp + 1));