Initial commit: C++ courseware

2.Course/2.深入浅出程序设计竞赛（提高篇）/最短路/C++源码/07_02_p1875.cpp

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+// P1875 魔法药水。每个原料位置独立选择制法，交换配方书写顺序不重复计数。
+// 当前原题提示同一对原料可能有不同产物，必须保存所有不同配方。
+#include <bits/stdc++.h>
+using namespace std;
+using ll = long long;
+ll addSat(ll a, ll b) { return a > LLONG_MAX - b ? LLONG_MAX : a + b; }
+ll mulSat(ll a, ll b) {
+    if (a == 0 || b == 0) return 0;
+    return a > LLONG_MAX / b ? LLONG_MAX : a * b;
+}
+struct Recipe { int a, b, c; };
+int main() {
+    ios::sync_with_stdio(false); cin.tie(nullptr);
+    int n; if (!(cin >> n)) return 0;
+    vector<ll> d(n), ways(n, 1);
+    for (ll &x : d) cin >> x;
+    vector<Recipe> rec;
+    vector<vector<int>> incident(n);
+    unordered_set<ll> seen;
+    int a, b, c;
+    while (cin >> a >> b >> c) {
+        if (a > b) swap(a, b);
+        ll key = (1LL * a * n + b) * n + c;
+        if (!seen.insert(key).second) continue;
+        int id = (int)rec.size(); rec.push_back({a, b, c});
+        incident[a].push_back(id); incident[b].push_back(id);
+    }
+    vector<int> need(rec.size(), 2);
+    vector<bool> done(n, false);
+    for (int round = 0; round < n; ++round) {
+        int u = -1;
+        for (int i = 0; i < n; ++i)
+            if (!done[i] && (u == -1 || d[i] < d[u])) u = i;
+        done[u] = true;
+        for (int id : incident[u]) {
+            if (--need[id] != 0) continue;
+            auto [a, b, c] = rec[id];
+            ll nd = d[a] + d[b], cnt = mulSat(ways[a], ways[b]);
+            if (nd < d[c]) { d[c] = nd; ways[c] = cnt; }
+            else if (nd == d[c]) ways[c] = addSat(ways[c], cnt);
+        }
+    }
+    cout << d[0] << ' ' << ways[0] << '\n';
+}