题目描述

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

Example 1:

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

Example 2:

Input:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

思路

维护四个边界的值，按照顺序依次打印。 对应的有字节的面试题，逆时针打印矩阵。

代码

class Solution {
          
   
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
          
   
        if (matrix.empty()) return {
          
   };
        int n = matrix.size();
        int m = matrix[0].size();
        int left = 0, right = m-1;
        int top = 0, bottom = n-1;
        
        vector<int> res;
        while(true) {
          
   
            for (int i=left; i<=right; i++) res.push_back(matrix[top][i]);
            top++;
            if (top > bottom) break;
            for (int i=top; i<=bottom; i++) res.push_back(matrix[i][right]);
            right--;
            if (left > right) break;
            for (int i=right; i>=left; --i) res.push_back(matrix[bottom][i]);
            bottom--;
            if (top > bottom) break;
            for (int i=bottom; i>=top; --i) res.push_back(matrix[i][left]);
            left++;
            if (left > right) break;
        }
        
        return res;
    }
};