【LeetCode】59. Spiral Matrix II

问题描述

https://leetcode.com/problems/spiral-matrix-ii/#/description

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 ]]

输入一个数n，输出从1到n^2的螺旋排序矩阵。

算法

直接按照从左到右、从上到下、从右到左、从下到上的顺序一个个数的填充数组即可。

代码

public int[][] generateMatrix(int n) {            if(n<=0) return new int[][]{};            int[][] res = new int[n][n];            // 开始填入数字            int rowBegin = 0, rowEnd = n-1;            int colBegin = 0, colEnd = n-1;            int index = 1;            while(rowBegin<=rowEnd || colBegin<=colEnd) {                // 从左到右                for(int i=colBegin;i<=colEnd;i++) {                    res[rowBegin][i] = index++;                }                rowBegin++;                // 从上到下                for(int i=rowBegin;i<=rowEnd;i++) {                    res[i][colEnd] = index++;                }                colEnd--;                // 从右到左                if(colEnd>=colBegin) {                    for(int i=colEnd;i>=colBegin;i--) {                        res[rowEnd][i] = index++;                    }                }                rowEnd--;                // 从下到上                if(rowEnd >=rowBegin) {                    for(int i=rowEnd;i>=rowBegin;i--) {                        res[i][colBegin] = index++;                    }                }                colBegin++;            }            return res;        }

LeetCode解题代码仓库：https://github.com/zgljl2012/leetcode-java