https://oj.leetcode.com/problems/spiral-matrix/

Spiral Matrix.java

public class Solution {
    public ArrayList<Integer> spiralOrder(int[][] matrix) {
        ArrayList<Integer> ret = new ArrayList<Integer>();
        int m = matrix.length;
        if (m == 0) return ret; 
        int n = matrix[0].length;
        int i = 0;
        int j = 0;
        int count = 0;
        int way = 1; // 1 right 2 down 3 left 4 right
        while (count < m * n){
            count++;
            ret.add(matrix[i][j]);
            matrix[i][j] = 0;
            if (way == 1){
                if ((j + 1 < n) && (matrix[i][j + 1] != 0)){
                    j++;
                } else {
                    way = 2;
                    i++;
                }
            }else if (way == 2){
                if ((i + 1 < m) && (matrix[i + 1][j] != 0)){
                    i++;
                } else {
                    way = 3;
                    j--;
                }
            }else if (way == 3){
                if ((j - 1 >= 0) && (matrix[i][j - 1] != 0)){
                    j--;
                } else {
                    way = 4;
                    i--;
                }
            }else if (way == 4){
                if ((i - 1 >= 0) && (matrix[i - 1][j] != 0)){
                    i--;
                } else {
                    way = 1;
                    j++;
                }
            }
        }
        return ret;
    }
}

哈哈别忘了考虑[]
matrix[0].length 存在的条件是matrix.length != 0~