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#include <bits/stdc++.h>
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using namespace std;
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const int INF = 0x3f3f3f3f;
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typedef pair<int, int> PII;
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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 = N << 1; //边数
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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 dist[15][N], st[15][N];
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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[0][s] = 0; //第零层，起点s
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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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int r = u / n; //行
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u %= n; //列
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if (st[r][u]) continue;
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st[r][u] = true;
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//更新同行,不使用免费机会
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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[r][j]) continue;
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if (dist[r][j] > dist[r][u] + w[i]) {
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dist[r][j] = dist[r][u] + w[i];
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q.push({dist[r][j], j + r * n});
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}
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}
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//更新下一行，使用免费机会
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if (r < k) {
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//出发点u,目标点：下一行的j位置
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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[r + 1][j]) continue; //下一行，j列走过吗?
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if (dist[r + 1][j] > dist[r][u]) { //从r,u直接通过零成本过来 (r+1,j)
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dist[r + 1][j] = dist[r][u];
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q.push({dist[r + 1][j], j + (r + 1) * n});
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}
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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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while (~scanf("%d%d%d", &n, &m, &k)) {
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memset(h, -1, sizeof(h));
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memset(dist, 0x3f, sizeof(dist));
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memset(st, false, sizeof(st));
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idx = 0;
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scanf("%d%d", &s, &t);
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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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add(a, b, c), add(b, a, c);
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}
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dijkstra();
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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[i][t]);
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printf("%d\n", ans);
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}
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return 0;
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} |
