洛谷 P4568 [JLOI2011]飞行路线

传送门

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(2e5 + 10);
const int maxm(3e6 + 10);
int ecnt, head[maxn];
bool vis[maxn];
int dis[maxn];

struct edge {
    int to, wt, nxt;
} edges[maxm];

template<typename T = int>
inline const T read()
{
    T x = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        x = (x << 3) + (x << 1) + ch - '0';
        ch = getchar();
    }
    return x * f;
}

template<typename T>
inline void write(T x, bool ln)
{
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10, false);
    putchar(x % 10 + '0');
    if (ln) putchar(10);
}

void addEdge(int u, int v, int w, bool d)
{
    edges[ecnt].to = v;
    edges[ecnt].wt = w;
    edges[ecnt].nxt = head[u];
    head[u] = ecnt++;
    if (d) addEdge(v, u, w, false);
}

int dijkstra(int src, int des, int k, int n)
{
    priority_queue<p, vector<p>, greater<p>> q;
    q.push(p(0, src));
    dis[src] = 0;
    while (not q.empty()) {
        int u = q.top().second;
        q.pop();
        if (vis[u]) continue;
        vis[u] = true;
        for (int i = head[u]; compl i; i = edges[i].nxt) {
            int v = edges[i].to, w = edges[i].wt;
            if (dis[v] > dis[u] + w) {
                dis[v] = dis[u] + w;
                q.push(p(dis[v], v));
            }
        }
    }
    return dis[des + k * n];
}

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("input.txt", "r", stdin);
#endif
    memset(head, -1, sizeof head);
    memset(dis, 0x3f, sizeof dis);
    int n = read(), m = read(), k = read();
    int s = read(), t = read();
    while (m--) {
        int u = read(), v = read(), w = read();
        addEdge(u, v, w, true);
        for (int i = 0; i < k; ++i) {
            addEdge(u + i * n, v + (i + 1) * n, 0, false);
            addEdge(v + i * n, u + (i + 1) * n, 0, false);
            addEdge(u + (i + 1) * n, v + (i + 1) * n, w, true);
        }
    }
    for (int i = 0; i < k; ++i) {
        addEdge(t + i * n, t + (i + 1) * n, 0, false);
    }
    write(dijkstra(s, t, k, n), true);
    return 0;
}