[LeetCode] 59. Spiral Matrix II 螺旋矩阵 II

Given an integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

与 54. Spiral Matrix 类似，这次给定一个整数n，以螺旋顺序填充元素到n^2的矩阵。

Java:

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        int k = 1;
        int top = 0, bottom = n - 1, left = 0, right = n - 1;
        while (left < right && top < bottom) {
            for (int j = left; j < right; j++) {
                res[top][j] = k++;
            }
            for (int i = top; i < bottom; i++) {
                res[i][right] = k++;
            }
            for (int j = right; j > left; j--) {
                res[bottom][j] = k++;
            }
            for (int i = bottom; i > top; i--) {
                res[i][left] = k++;
            }
            left++;
            right--;
            top++;
            bottom--;
        }
        if (n % 2 != 0)
            res[n / 2][n / 2] = k;
        return res;
    }
}

Python:

class Solution:
    # @param matrix, a list of lists of integers
    # @return a list of integers
    def spiralOrder(self, matrix):
        result = []
        if matrix == []:
            return result

        left, right, top, bottom = 0, len(matrix[0]) - 1, 0, len(matrix) - 1

        while left <= right and top <= bottom:
            for j in xrange(left, right + 1):
                result.append(matrix[top][j])
            for i in xrange(top + 1, bottom):
                result.append(matrix[i][right])
            for j in reversed(xrange(left, right + 1)):
                if top < bottom:
                    result.append(matrix[bottom][j])
            for i in reversed(xrange(top + 1, bottom)):
                if left < right:
                    result.append(matrix[i][left])
            left, right, top, bottom = left + 1, right - 1, top + 1, bottom - 1

        return result　

C++：

class Solution {
public:
    vector<vector<int> > generateMatrix(int n) {
        vector<vector<int> > res(n, vector<int>(n, 1));
        int val = 1, p = n;
        for (int i = 0; i < n / 2; ++i, p -= 2) {
            for (int col = i; col < i + p; ++col)
                res[i][col] = val++;
            for (int row = i + 1; row < i + p; ++row)
                res[row][i + p - 1] = val++;
            for (int col = i + p - 2; col >= i; --col)
                res[i + p - 1][col] = val++;
            for (int row = i + p - 2; row > i; --row)
                res[row][i] = val++;
        }
        if (n % 2 != 0) res[n / 2][n / 2] = val;
        return res;
    }
};

　　

类似题目：

[LeetCode] 54. Spiral Matrix 螺旋矩阵

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