careercup题目20131010

Spiraly print n*n matrix. 
Eg: [1,2,3,4] 
[12,13,14,5] 
[11,16,15,6] 
[10,9,8,7] 

Should print 
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16

螺旋输出n*n矩阵

分析：n*n矩阵可分为n-2层输出，每层按照顺时针方向输出，每层输出的开始元素下标为 A[i][i]

public class PrintMatrix {

    /**
     * question：
     * Spiraly print n*n matrix. 
        Eg: [1,2,3,4] 
        [12,13,14,5] 
        [11,16,15,6] 
        [10,9,8,7] 
        
        Should print 
        1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
     */
    public static void main(String[] args) {
        int[][] A = { { 1,  2,  3,  4 }, 
                  { 12, 13, 14, 5 }, 
                  { 11, 16, 15, 6 },
                  { 10,  9,  8, 7 } };
        int[][] B ={{ 0,  1,  2,  3, 4},
          {15, 16, 17, 18, 5},
          {14, 23, 24, 19, 6},
          {13, 22, 21, 20, 7},
          {12, 11, 10, 9, 8}};
        System.out.println(printMatrix(A));
        System.out.println(printMatrix(B));
    }
    
    public static String printMatrix(int[][] A){
        StringBuffer sb = new StringBuffer();
        int n = A.length;
        for(int i=0;i<n-2;i++){
            for(int j=i;j<n-i-1;j++){
                sb.append(String.valueOf(A[i][j])).append(" ");
            }
            for(int j=i;j<n-i-1;j++){
                sb.append(String.valueOf(A[j][n-i-1])).append(" ");
            }
            for(int j=n-i-1;j>i;j--){
                sb.append(String.valueOf(A[n-i-1][j])).append(" ");
            }
            for(int j=n-i-1;j>i;j--){
                sb.append(String.valueOf(A[j][i])).append(" ");
            }
        }
        return sb.toString();
    }

}