矩阵旋转90度的两种方法

java语言：

第一种：

public static void rotate(char a[][],int N){    int layer;    for(layer=0; layer<N/2; layer++)    {        int first = layer;                      int last = N-1-layer;                       int i;        for(i=layer; i<last; i++)        {                int offset = i-layer;                char top = a[first][i];                a[first][i] = a[last-offset][first];                a[last-offset][first] = a[last][last-offset];                a[last][last-offset] = a[i][last];                a[i][last] = top;        }    }}