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| class Solution {
private static class UnionFind {
private final int[] parent;
public UnionFind(int n) {
this.parent = new int[n];
for (int i = 0; i < parent.length; i++) {
parent[i] = i;
}
}
public void union(int x, int y) {
int xRoot = getRoot(x), yRoot = getRoot(y);
if (xRoot == yRoot) {
return;
}
parent[xRoot] = yRoot;
}
private int getRoot(int x) {
if (parent[x] != x) {
parent[x] = getRoot(parent[x]);
}
return parent[x];
}
}
private static final int[][] DIRECTIONS = new int[][]{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
public int countSubIslands(int[][] grid1, int[][] grid2) {
int m = grid1.length, n = grid1[0].length;
UnionFind unionFind = new UnionFind(m * n);
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (grid1[i][j] == 1) {
dfs(grid1, unionFind, i, j);
}
}
}
int count = 0;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (grid2[i][j] == 1) {
int root = unionFind.getRoot(toIndex(n, i, j));
if (dfsCheck(grid1, grid2, unionFind, root, i, j)) {
count++;
}
}
}
}
return count;
}
private boolean dfsCheck(int[][] grid1, int[][] grid2, UnionFind unionFind, int root, int i, int j) {
int m = grid2.length, n = grid2[0].length;
boolean result = grid1[i][j] == 2;
grid2[i][j] = 2;
for (int[] direction : DIRECTIONS) {
int nextI = i + direction[0], nextJ = j + direction[1];
if (nextI >= 0 && nextI < m && nextJ >= 0 && nextJ < n && grid2[nextI][nextJ] == 1) {
if (grid1[nextI][nextJ] != 2 || unionFind.getRoot(toIndex(n, nextI, nextJ)) != root) {
result = false;
}
result &= dfsCheck(grid1, grid2, unionFind, root, nextI, nextJ);
}
}
return result;
}
private void dfs(int[][] grid1, UnionFind unionFind, int i, int j) {
int m = grid1.length, n = grid1[0].length;
grid1[i][j] = 2;
for (int[] direction : DIRECTIONS) {
int nextI = i + direction[0], nextJ = j + direction[1];
if (nextI >= 0 && nextI < m && nextJ >= 0 && nextJ < n && grid1[nextI][nextJ] == 1) {
unionFind.union(toIndex(n, i, j), toIndex(n, nextI, nextJ));
dfs(grid1, unionFind, nextI, nextJ);
}
}
}
private int toIndex(int n, int i, int j) {
return i * n + j;
}
}
|