LeetCode in Net

54. Spiral Matrix

Medium

Given an m x n matrix, return all elements of the matrix in spiral order.

Example 1:

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

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

Example 2:

Input: matrix = [[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]

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 10
• -100 <= matrix[i][j] <= 100

Solution

using System.Collections.Generic;

public class Solution {
    public IList<int> SpiralOrder(int[][] matrix) {
        var res = new List<int>();
        if (matrix == null || matrix.Length == 0) {
            return res;
        }
        int m = matrix.Length;
        int n = matrix[0].Length;
        int top = 0;
        int bottom = m - 1;
        int left = 0;
        int right = n - 1;
        while (top <= bottom && left <= right) {
            for (int j = left; j <= right; j++) {
                res.Add(matrix[top][j]);
            }
            top++;
            for (int i = top; i <= bottom; i++) {
                res.Add(matrix[i][right]);
            }
            right--;
            if (top <= bottom) {
                for (int j = right; j >= left; j--) {
                    res.Add(matrix[bottom][j]);
                }
                bottom--;
            }
            if (left <= right) {
                for (int i = bottom; i >= top; i--) {
                    res.Add(matrix[i][left]);
                }
                left++;
            }
        }
        return res;
    }
}

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