# 0054. Spiral Matrix
###### tags: `Leetcode` `Microsoft` `Medium`
Link: https://leetcode.com/problems/spiral-matrix/
## 思路
一圈圈遍历
## Code

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> ans = new ArrayList<>();
        if(matrix.length == 0 || matrix[0].length == 0){
            return ans;
        }
        int top = 0, bottom = matrix.length-1, left = 0, right = matrix[0].length-1;
        while(top<=bottom && left<= right){
            for(int i = left;i <= right;i++){
                ans.add(matrix[top][i]);
            }
            for(int i = top+1;i <= bottom;i++){
                ans.add(matrix[i][right]);
            }
            if(top<bottom && left<right){
                for(int i = right-1; i >= left;i--){
                    ans.add(matrix[bottom][i]);
                }
                for(int i = bottom-1; i > top;i--){
                    ans.add(matrix[i][left]);
                }
            }
            top++;
            bottom--;
            left++;
            right--;
        }
        return ans;
    }
}