[LeetCode]59.螺旋矩阵II

class Solution {
    public int[][] generateMatrix(int n) {
        int end = n * n;
        int counter = 1;
        int[][] res = new int[n][n];
        boolean[][] visited = new boolean[n][n];
        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        int i = 0;
        int j = 0;
        int directionIndex = 0;
        while(counter <= end){
            res[i][j] = counter;
            visited[i][j] = true;
            counter ++;
            int nextI = i + directions[directionIndex][0];
            int nextJ = j + directions[directionIndex][1];
            if(nextI < 0 || nextI >= n || nextJ < 0 || nextJ >=n || visited[nextI][nextJ]){
                directionIndex = (directionIndex + 1) % 4;
            }
            i += directions[directionIndex][0];
            j += directions[directionIndex][1];

        }
        return res;
    }
}

本题的思路和螺旋矩阵类似，通过方向数组和边界判断实现螺旋转向。

另外，不需要使用 visited 函数确定是否访问过该点，而是直接根据 res[nextI][nextJ] > 0 来判断。