面试题 29. 顺时针打印矩阵

题目描述

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

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]

题解

从外往里一圈一圈遍历并存储矩阵元素即可。

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        int rows = matrix.size(), cols = matrix[0].size();
        if (rows == 0 || cols == 0) return {};

        vector<int> res;
        int top = 0, bottom = rows -1, left = 0, right = cols - 1;
        while (top <= bottom && left <= right) {
            for (int i = left; i <= right; i++) res.push_back(matrix[top][i]);
            for (int i = top + 1; i <= bottom; i++) res.push_back(matrix[i][right]);
            // 判断不可少
            if (left < right && top < bottom) {
                for (int i = right - 1; i >= left; i--) res.push_back(matrix[bottom][i]);
                // 可以模拟发现 不可以为 i >= top
                for (int i = bottom - 1; i > top; i--) res.push_back(matrix[i][left]);
            }
            top++;
            bottom--;
            left++;
            right--;
        }
        return res;
    }
};