题目
https://leetcode.com/problems/all-paths-from-source-to-target/
题解
回溯,中规中矩,直接上代码。
class Solution {
int N;
public List<List<Integer>> allPathsSourceTarget(int[][] graph) {
N = graph.length;
boolean[][] g = new boolean[N][N];
for (int i = 0; i < N; i++) {
for (int j : graph[i]) {
g[i][j] = true;
}
}
return process(g, 0, new HashSet<>());
}
// 从 i 出发,到达 n-1 的全部路径
public List<List<Integer>> process(boolean[][] g, int i, Set<Integer> seen) {
List<List<Integer>> result = new ArrayList<>();
if (i == N - 1) { // 已到终点
result.add(new ArrayList<>());
result.get(0).add(N - 1);
return result;
} else { // 未到终点
for (int j = 0; j < N; j++) { // i -> j -> N-1
if (g[i][j] && !seen.contains(j)) {
// backtracing
seen.add(j);
for (List<Integer> path : process(g, j, seen)) {
List<Integer> list = new ArrayList<>();
list.add(i);
list.addAll(path);
result.add(list);
}
seen.remove(j);
}
}
}
return result;
}
}