59. Spiral Matrix II

最新推荐文章于 2019-04-20 16:41:07 发布

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最新推荐文章于 2019-04-20 16:41:07 发布

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分类专栏： LeetCode Array 文章标签： LeetCode Array Spiral Matrix II

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Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

解题思路类似于Spiral Matrix I，螺旋遍历，只是这里因为是n*n的矩阵，所以不用做代码中的判断：

public class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        if (n < 1) {
            return res;
        }
        int rowBegin = 0, rowEnd = n - 1;
        int colBegin = 0, colEnd = n - 1;
        int num = 1;
        while (rowBegin <= rowEnd && colBegin <= colEnd) {
            for (int i = colBegin; i <= colEnd; i ++) {
                res[rowBegin][i] = num;
                num ++;
            }
            rowBegin ++;
            for (int i = rowBegin; i <= rowEnd; i ++) {
                res[i][colEnd] = num;
                num ++;
            }
            colEnd --;
            //if (rowBegin <= rowEnd) {
                for (int i = colEnd; i >= colBegin; i --) {
                    res[rowEnd][i] = num;
                    num ++;
                }
                rowEnd --;
            //}
            //if (colBegin <= colEnd) {
                for (int i = rowEnd; i >= rowBegin; i --) {
                    res[i][colBegin] = num;
                    num ++;
                }
                colBegin ++;
            //}
        }
        return res;
    }
}