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58 lines
1.2 KiB
58 lines
1.2 KiB
#include <bits/stdc++.h>
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using namespace std;
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const int N = 2010;
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const int M = 2e5 + 10;
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typedef pair<double, int> PDI; // 堆中数值是浮点数，注意区别
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int n, m;
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double dis[N];
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bool st[N];
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int h[N], e[M], ne[M], idx;
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double w[M]; // 边权为浮点数,与一般的题目有区别
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void add(int a, int b, double c) {
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e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
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}
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int S, T;
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void dijkstra() {
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priority_queue<PDI> q; // 大顶堆
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dis[S] = 1;
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q.push({1, S});
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while (q.size()) {
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auto t = q.top();
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q.pop();
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int u = t.second;
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if (st[u]) continue;
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st[u] = true;
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for (int i = h[u]; ~i; i = ne[i]) {
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int v = e[i];
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double a = 1 - w[i];
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if (dis[v] < dis[u] * a) {
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dis[v] = dis[u] * a;
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q.push({dis[v], v});
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}
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}
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}
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}
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int main() {
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memset(h, -1, sizeof h);
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cin >> n >> m;
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while (m--) {
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int a, b, c;
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cin >> a >> b >> c;
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double w = c * 0.01;
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add(a, b, w), add(b, a, w);
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}
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cin >> S >> T;
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dijkstra();
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printf("%.8lf\n", 100 / dis[T]);
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return 0;
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} |