1559. 二维网格图中探测环(leetcode)

1559. 二维网格图中探测环

class Solution {int[] dx={0,1,0,-1};int[] dy={1,0,-1,0};int n;int m;char[][] grid;boolean[][] vis;int startx;int starty;boolean canRing;public boolean containsCycle(char[][] grid) {// 能否连成环 关键是 移动后能回到起始点位置m=grid.length;n=grid[0].length;vis=new boolean[m][n];this.grid=grid;for(int i=0;i<m;i++)for(int j=0;j<n;j++){if(vis[i][j]==true)continue;                            dfs(i,j,new int[]{-1,-1}); // 上一步不存在if(canRing) return canRing;}return canRing;}void dfs(int x,int y,int[] lastPoint){if(vis[x][y]==true){canRing = true;return;}vis[x][y]=true;for(int i=0;i<4;i++){int a=dx[i]+x,b=dy[i]+y;if(a==lastPoint[0] && b==lastPoint[1])continue;if(a>=0 && b>=0 && a<m && b<n && grid[a][b]==grid[x][y]){dfs(a,b,new int[]{x,y});}}}
}