Leetcode 54. Spiral Matrix

54. Spiral Matrix

• Total Accepted: 66779
• Total Submissions: 286442
• Difficulty: Medium

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

You should return [1,2,3,6,9,8,7,4,5].

思路：模拟，一圈圈地环绕，直到停止。

代码：

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> res;
        if(matrix.size()==0) return res;
        if(matrix[0].size()==0) return res;
        int m=matrix.size(),n=matrix[0].size(),i=0,j=0;
        while(n>0&&m>0){
            res.push_back(matrix[i][j]);
            n--;
            m--;
            int step=n;
            while(step>0){
                res.push_back(matrix[i][++j]);
                step--;
            }
            step=m;
            while(step>0){
                res.push_back(matrix[++i][j]);
                step--;
            }
            if(m>0&&n>0){//判断有没有剩余的半圈
                step=n--;//得到下一圈的n
                while(step>0){
                    res.push_back(matrix[i][--j]);
                    step--;
                }
                step=--m;//得到下一圈的m
                while(step>0){
                    res.push_back(matrix[--i][j]);
                    step--;
                }
                j++;
            }
        }
        return res;
    }
};