python/TangDou/AcWing/MiniPath/P4568_2.cpp

#include <bits/stdc++.h>
using namespace std;

const int INF = 0x3f3f3f3f;
typedef pair<int, int> PII;

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
const int M = N << 1;            //边数
//邻接表
int e[M], h[N], idx, w[M], ne[M];
void add(int a, int b, int c) {
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}

int dist[15][N], st[15][N];
int n, m, s, t, k;

void dijkstra() {
    priority_queue<PII, vector<PII>, greater<PII>> q;
    dist[0][s] = 0; //第零层，起点s
    q.push({0, s});

    while (q.size()) {
        int u = q.top().second;
        q.pop();

        int r = u / n; //行
        u %= n;        //列
        if (st[r][u]) continue;
        st[r][u] = true;

        //更新同行,不使用免费机会
        for (int i = h[u]; ~i; i = ne[i]) {
            int j = e[i];
            if (st[r][j]) continue;
            if (dist[r][j] > dist[r][u] + w[i]) {
                dist[r][j] = dist[r][u] + w[i];
                q.push({dist[r][j], j + r * n});
            }
        }
        //更新下一行，使用免费机会
        if (r < k) {
            //出发点u,目标点：下一行的j位置
            for (int i = h[u]; ~i; i = ne[i]) {
                int j = e[i];
                if (st[r + 1][j]) continue;        //下一行，j列走过吗?
                if (dist[r + 1][j] > dist[r][u]) { //从r,u直接通过零成本过来 (r+1,j)
                    dist[r + 1][j] = dist[r][u];
                    q.push({dist[r + 1][j], j + (r + 1) * n});
                }
            }
        }
    }
}

int main() {
    while (~scanf("%d%d%d", &n, &m, &k)) {
        memset(h, -1, sizeof(h));
        memset(dist, 0x3f, sizeof(dist));
        memset(st, false, sizeof(st));
        idx = 0;

        scanf("%d%d", &s, &t);
        while (m--) {
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            add(a, b, c), add(b, a, c);
        }
        dijkstra();

        int ans = INF;
        for (int i = 0; i <= k; i++)
            ans = min(ans, dist[i][t]);
        printf("%d\n", ans);
    }
    return 0;
}