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myCpps/almostShortestPath_UVA12144OJ.cpp

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+#include <bits/stdc++.h>
+
+using namespace std;
+
+
+const int inf = INT_MAX / 2;
+
+struct segment
+{
+    int u;
+    int p;
+
+    bool operator < (const segment & temp) const
+    {
+        return p > temp.p;
+    }
+};
+segment _segment(int u, int p)
+{
+    segment temp{u, p}; return temp;
+}
+
+struct edge
+{
+    int u;
+    int v;
+};
+edge _edge(int u, int v)
+{
+    edge temp{u, v}; return temp;
+}
+
+void erasePath(int u, vector<vector<int>> & a, vector<set<int>> & f)
+{
+    for (auto it = f[u].begin(); it != f[u].end(); ++it)
+    {
+        int v = *it;
+
+        a[v][u] = inf;
+        erasePath(v, a, f);
+    }
+}
+
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	std::cin.tie(NULL);
+    while (true)
+    {
+        int n = 0, m = 0; cin >> n >> m;
+        if (n + m == 0) break;
+
+        vector<vector<int>> a(n, vector<int>(n, inf));
+
+        int s, e; cin >> s >> e;
+
+        for (int c = 1; c <= m; ++c)
+        {
+            int u, v, p; cin >> u >> v >> p;
+            a[u][v] = p;
+        }
+
+        vector<int> d(n, inf);
+        priority_queue<segment> pq; pq.push(_segment(s, 0));
+        vector<set<int>> f(n);
+        while (pq.empty() == false)
+        {
+            segment now = pq.top(); pq.pop();
+
+            for (int v = 0; v <= n - 1; ++v)
+            {
+                if (a[now.u][v] == inf) continue;
+
+                segment next;
+                next.u = v;
+                next.p = now.p + a[now.u][v];
+
+                if (next.p < d[next.u])
+                {
+                    d[next.u] = next.p;
+                    f[v].clear();
+                    f[v].insert(now.u);
+
+                    pq.push(next);
+                }
+                else if (next.p == d[next.u])
+                {
+                    f[v].insert(now.u);
+                }
+            }
+        }
+
+        f[s].clear();
+        erasePath(e, a, f);
+
+        vector<int> _d(n, inf);
+        priority_queue<segment> _pq; _pq.push(_segment(s, 0));
+        while (_pq.empty() == false)
+        {
+            segment now = _pq.top(); _pq.pop();
+
+            for (int v = 0; v <= n - 1; ++v)
+            {
+                if (a[now.u][v] == inf) continue;
+
+                segment next;
+                next.u = v;
+                next.p = now.p + a[now.u][v];
+
+                if (next.p < _d[next.u])
+                {
+                    _d[next.u] = next.p;
+                    _pq.push(next);
+                } 
+            }
+        }
+
+        if (_d[e] == inf)
+        {
+            cout << "-1\n";
+        }
+        else
+        {
+            cout << _d[e] << '\n';
+        }
+    }
+
+   	cout.flush();
+   	return 0;
+}
+