feat: new graph problems formatted.

quase-menor-caminho/src/ac.cpp

@@ -0,0 +1,70 @@
+#include <bits/stdc++.h>
+
+#define INF 0x7FFFFFFF
+using namespace std;
+
+using ll = long long;
+using pll = pair<ll, ll>;
+using graph = vector<vector<pll>>;
+const int MAXN = 510;
+
+vector<ll> dijk(int x, graph& g) {
+    priority_queue<pll> pq;
+    pq.push({0, x});
+    vector<ll> dist(MAXN, INF);
+    while (pq.size()){
+        auto [w, v] = pq.top();
+        pq.pop();
+        w = -w;
+        if (dist[v] <= w) continue;
+        dist[v] = w;
+        for (auto [u, ww] : g[v]) {
+            if (dist[u] <= w + ww) continue;
+            pq.push({-(w+ww), u});
+        }
+    }
+    return dist;
+}
+
+ll almost_dijk(int s, int d, graph& g, vector<ll>& dist_s, vector<ll>& dist_d) {
+    ll best = dist_s[d];
+    if (best == INF) return -1;
+
+    priority_queue<pll> pq;
+    pq.push({0, s});
+    vector<ll> dist(MAXN, INF);
+    while (pq.size()){
+        auto [w, v] = pq.top();
+        pq.pop();
+        w = -w;
+        if (v == d) return w;
+        if (dist[v] <= w) continue;
+        dist[v] = w;
+        for (auto [u, ww] : g[v]) {
+            if (dist_s[v] + ww + dist_d[u] <= best) continue; // pula essa aresta, corresponde a um caminho minimo
+            if (dist[u] <= w + ww) continue;
+            pq.push({-(w+ww), u});
+        }
+    }
+    return -1;
+}
+
+int main(){
+    ios::sync_with_stdio(0);
+    cin.tie(0); cout.tie(0);
+
+    int n, m; 
+    while (cin>>n>>m, n!=0 && m!=0){
+        int s, d; cin >> s >> d;
+        vector<vector<pll>> g(MAXN);
+        vector<vector<pll>> g_rev(MAXN);
+        for (int i=0;i<m;i++){
+            int u,v,p; cin >> u >> v >> p;
+            g[u].push_back({v, p});
+            g_rev[v].push_back({u, p});
+        }
+        vector<ll> dist_s = dijk(s, g);
+        vector<ll> dist_d = dijk(d, g_rev);
+        cout << almost_dijk(s, d, g, dist_s, dist_d) << '\n';
+    }
+}