leetcode694.不同岛屿数量(java)

题目

思路
如果两个岛屿路径相同，则相同

具体代码

class Solution {
    public int numDistinctIslands(int[][] grid) {
        HashSet<String> set = new HashSet<>();
        for(int i = 0;i < grid.length;i++){
            for(int j = 0;j < grid[0].length;j++){
                if(grid[i][j]==0){
                    continue;
                }
                StringBuilder sb = new StringBuilder();
                dfs(grid,i,j,sb);
                set.add(sb.toString());
            }
        }
        return set.size();
    }
    public void dfs(int[][] grid,int i, int j, StringBuilder sb){
        if(i < 0 || i>=grid.length || j<0 || j>=grid[0].length ||grid[i][j]!=1){
            return;
        }
        grid[i][j] = 0;
        dfs(grid,i+1,j,sb.append("d"));
        dfs(grid,i,j+1,sb.append("r"));
        dfs(grid,i-1,j,sb.append("u"));
        dfs(grid,i,j-1,sb.append("l"));
    }
}

参考资料
https://leetcode-cn.com/problems/number-of-distinct-islands/solution/java-dfs-by-z446979478/