剑指Offer（十九）-- 顺时针打印矩阵

import java.util.ArrayList;
public class Solution {
    public ArrayList<Integer> printMatrix(int[][] matrix) {
        ArrayList<Integer> results = new ArrayList();
        if (matrix != null && matrix.length > 0) {
            int left = 0;
            int right = matrix[0].length - 1;
            int up = 0;
            int down = matrix.length - 1;
            int i;
            while (true) {
                for (i = left; i <= right; i++) {
                    results.add(matrix[up][i]);
                }
                if ((++up) > down) {
                    break;
                }
                for (i = up; i <= down; i++) {
                    results.add(matrix[i][right]);
                }
                if (--right < left) {
                    break;
                }
                for(i=right;i>=left;i--){
                    results.add(matrix[down][i]);
                }
                if(--down<up){
                    break;
                }
                for(i=down;i>=up;i--){
                    results.add(matrix[i][left]);
                }
                if(++left>right){
                    break;
                }
            }
        }
        return results;
    }
}