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leetcode 59 Solution

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代码解析

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package com.demo.s59;

/**
 * 螺旋矩阵 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 。
 */
public class Solution {
    public int[][] generateMatrix(int n) {
        int maxNum = n * n;
        int curNum = 1;
        //返回值数组
        int[][] matrix = new int[n][n];
        int row = 0, column = 0;
        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}}; // 右下左上
        int directionIndex = 0;
        while (curNum <= maxNum) {
            matrix[row][column] = curNum;
            curNum++;
            //行
            int nextRow = row + directions[directionIndex][0],
                    //列
                    nextColumn = column + directions[directionIndex][1];
            //行列边界判断，需要调整方向
            if (nextRow < 0 || nextRow >= n || nextColumn < 0 || nextColumn >= n || matrix[nextRow][nextColumn] != 0) {
                // 顺时针旋转至下一个方向
                directionIndex = (directionIndex + 1) % 4;
            }
            row = row + directions[directionIndex][0];
            column = column + directions[directionIndex][1];
        }
        return matrix;
    }
}