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#include <bits/stdc++.h>
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using namespace std;
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const int N = 1e4 * 2 * 11 + 10; //节点数：1e4,无向图，1e4*2,共k+1(k<=10)层:1e4*2*11
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const int M = 5e4 * 11 * 3 + 10; //边数
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typedef pair<int, int> PII;
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const int INF = 0x3f3f3f3f;
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int dist[N], st[N];
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//邻接表
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int e[M], h[N], idx, w[M], ne[M];
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void add(int a, int b, int c) {
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e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
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}
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int n, m, s, t, k;
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void dijkstra() {
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priority_queue<PII, vector<PII>, greater<PII>> q;
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dist[s] = 0;
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q.push({0, s});
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while (q.size()) {
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int u = q.top().second;
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q.pop();
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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 j = e[i];
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if (st[j]) continue;
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if (dist[j] > dist[u] + w[i]) {
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dist[j] = dist[u] + w[i];
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q.push({dist[j], j});
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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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//多组测试数据
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while (~scanf("%d%d%d", &n, &m, &k)) {
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//初始化
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memset(h, -1, sizeof(h));
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idx = 0;
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memset(dist, 0x3f, sizeof(dist));
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memset(st, false, sizeof(st));
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scanf("%d%d", &s, &t); //起点与终点
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while (m--) {
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int a, b, c;
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scanf("%d%d%d", &a, &b, &c);
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//分层图建图
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for (int i = 0; i <= k; i++) { //创建k+1层分层图
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add(a + i * n, b + i * n, c), add(b + i * n, a + i * n, c); //无向图
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if (i < k) //从第0层开始，到k-1层结束，都需要向下一层建立通道
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add(a + i * n, b + (i + 1) * n, 0), add(b + i * n, a + (i + 1) * n, 0);
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}
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}
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//一遍最短路
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dijkstra();
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// k+1个层中，都去找t的最短路径，再取最小值，就是答案
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int ans = INF;
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for (int i = 0; i <= k; i++)
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ans = min(ans, dist[t + i * n]);
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printf("%d\n", ans);
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}
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return 0;
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} |
