题目

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字。

示例 1：

输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[1,2,3,6,9,8,7,4,5]

示例 2：

输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
输出：[1,2,3,4,8,12,11,10,9,5,6,7]

限制：

• 0 <= matrix.length <= 100
• 0 <= matrix[i].length <= 100

本题同【LeetCode】54. 螺旋矩阵

思路

依次从四个方向判断。

代码

时间复杂度：O(n*m)
空间复杂度：O(1)

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