leetcode题目59. 螺旋矩阵 II

题目描述

链接：https://leetcode-cn.com/problems/spiral-matrix-ii/
给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

示例

输入：n = 3
输出：[[1,2,3],[8,9,4],[7,6,5]]

代码

    public int[][] generateMatrix(int n) {
        if (n <= 0) {
            return null;
        }
        int[][] result = new int[n][n];

        int totalCount = n * n;
        int curFillCount = 1;
        int left = 0;
        int right = n - 1;
        int top = 0;
        int bottom = n - 1;
        while (curFillCount <= totalCount) {
            for (int i = left; i <= right && (curFillCount <= totalCount); i++) {
                result[top][i] = curFillCount;
                curFillCount ++;
            }
            top ++;

            for (int i = top; i <= bottom && (curFillCount <= totalCount); i++) {
                result[i][right] = curFillCount;
                curFillCount ++;
            }
            right --;

            for (int i = right; i >= left && (curFillCount <= totalCount); i--) {
                result[bottom][i] = curFillCount;
                curFillCount ++;
            }
            bottom --;

            for (int i = bottom; i >= top && (curFillCount <= totalCount); i--) {
                result[i][left] = curFillCount;
                curFillCount ++;
            }
            left ++;
        }

        return result;
    }