博文中会简要介绍Leetcode P0059题目分析及解题思路。
“Spiral Matrix II”是p0054的变形题，基本思路一致。
Given a positive integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.
以下是Java的题解代码实现。
class Solution {
public int[][] generateMatrix(int n) {
boolean[][] visited = new boolean[n][n];
int[][] matrix = new int[n][n];
int count = 1, r = 0, c = 0, di = 0;
while (count <= n*n) {
matrix[r][c] = count;
visited[r][c] = true;
if (this.isRequiredToTurn(visited, r+dr[di], c+dc[di], n, n))
di = (di+1)%4;
r += dr[di];
c += dc[di];
++count;
}
return matrix;
}
private int[] dr = new int[] {0, 1, 0, -1};
private int[] dc = new int[] {1, 0, -1, 0};
private boolean isRequiredToTurn(boolean[][] visited, int nextRow, int nextCol, int row, int col) {
if (nextRow < row && nextRow >= 0
&& nextCol < col && nextCol >= 0
&& !visited[nextRow][nextCol]) {
return false;
}
return true;
}
}