Спиральный обход матрицы

Идея: Четыре сжимающиеся границы с проверкой перед нижней строкой и левым столбцом.

JavaScript:

class Solution {
    spiralOrder(matrix) {
        const res = [];
        let top = 0, bottom = matrix.length - 1;
        let left = 0, right = matrix[0].length - 1;
        while (top <= bottom && left <= right) {
            for (let j = left; j <= right; j++) res.push(matrix[top][j]);
            top++;
            for (let i = top; i <= bottom; i++) res.push(matrix[i][right]);
            right--;
            if (top <= bottom) { for (let j = right; j >= left; j--) res.push(matrix[bottom][j]); bottom--; }
            if (left <= right) { for (let i = bottom; i >= top; i--) res.push(matrix[i][left]); left++; }
        }
        return res;
    }
}

Python:

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        res = []
        top, bottom = 0, len(matrix) - 1
        left, right = 0, len(matrix[0]) - 1
        while top <= bottom and left <= right:
            for j in range(left, right + 1):
                res.append(matrix[top][j])
            top += 1
            for i in range(top, bottom + 1):
                res.append(matrix[i][right])
            right -= 1
            if top <= bottom:
                for j in range(right, left - 1, -1):
                    res.append(matrix[bottom][j])
                bottom -= 1
            if left <= right:
                for i in range(bottom, top - 1, -1):
                    res.append(matrix[i][left])
                left += 1
        return res

Java:

class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> res = new ArrayList<>();
        int top = 0, bottom = matrix.length - 1;
        int left = 0, right = matrix[0].length - 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;
    }
}