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| class Solution {
int[][] grid;
int m, n, cnt;
boolean[][] visited;
static int[][] dirs = new int[][]{{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
public int uniquePathsIII(int[][] grid) {
this.grid = grid;
m = grid.length;
n = grid[0].length;
visited = new boolean[m][n];
int x = 0, y = 0;
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
if (grid[i][j] == 0) ++cnt;
else if (grid[i][j] == 1) {
x = i;
y = j;
}
}
}
visited[x][y] = true;
return dfs(x, y, 0);
}
private int dfs(int x, int y, int k) {
if (grid[x][y] == 2) return k == cnt + 1 ? 1 : 0;
int ans = 0;
for (int[] dir : dirs) {
int nx = x + dir[0], ny = y + dir[1];
if (nx < 0 || nx >= m || ny < 0 || ny >= n || visited[nx][ny] || grid[nx][ny] == -1) continue;
visited[nx][ny] = true;
ans += dfs(nx, ny, k + 1);
visited[nx][ny] = false;
}
return ans;
}
}
|
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