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longestPath.cpp
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longestPath.cpp
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#include <iostream>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
void dfs(int u, int s, int t, const vector<vector<int>> &adj, bool *&visited, vector<int> &result) {
visited[u] = true;
for (int v : adj[u]) {
if (v == s) continue;
if (v == t) {
result[v] = max(result[v], result[u] + 1);
} else {
if (!visited[v]) {
result[v] = result[u] + 1;
dfs(v, s, t, adj, visited, result);
} else {
if (result[v] < result[u] + 1) {
result[v] = result[u] + 1;
dfs(v, s, t, adj, visited, result);
}
}
}
}
}
int longestPath(int n, std::vector<std::vector<int>> edges, int u, int v)
{
vector<vector<int>> adj(n + 1);
bool *visited = new bool[n + 1];
vector<int> result(n + 1, -1);
for (int i = 1; i <= n; i++) visited[i] = false;
queue<int> qu;
qu.push(u);
visited[u] = true;
result[u] = 0;
for (vector<int> x : edges) {
adj[x[0]].push_back(x[1]);
}
dfs(u, u, v, adj, visited, result);
return result[v];
}
int main() {
cout << longestPath(3, {{1, 2}, {2, 3}, {1, 3}}, 1, 3);
return 0;
}