USACO08JAN Telephone Lines

Luogu

分析

分层最短路模板题。

话说我卡了半天发现是 insert 函数写错了？？？

代码

#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define N 100001
#define il inline
#define re register
#define INF 0x3f3f3f3f
#define tie0 cin.tie(0),cout.tie(0)
#define fastio ios::sync_with_stdio(false)
#define File(x) freopen(x".in","r",stdin);freopen(x".out","w",stdout)
using namespace std;
typedef long long ll;

template <typename T> inline void read(T &x) {
    T f = 1; x = 0; char c;
    for (c = getchar(); !isdigit(c); c = getchar()) if (c == '-') f = -1;
    for ( ; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
    x *= f;
}

struct edge {
    int to, val, nxt;
} e[N];

struct node {
    int id, d;
    friend bool operator < (node x, node y) { return x.d > y.d; }
};

int n, m, k;
int head[N], cnt, dis[N];
bool inq[N];

void insert(int u, int v, int w) {
    e[++cnt].to = v, e[cnt].val = w, e[cnt].nxt = head[u], head[u] = cnt;
}

void add(int u, int v, int w) { insert(u, v, w), insert(v, u, w); }

void Dijkstra() {
    priority_queue <node> q;
    memset(dis, INF, sizeof dis);
    dis[1] = 0;
    q.push((node){1, 0});
    while (!q.empty()) {
        int u = q.top().id; q.pop();
        if (inq[u]) continue;
        inq[u] = 1;
        for (int i = head[u]; i; i = e[i].nxt) {
            int v = e[i].to, w = e[i].val;
            if (dis[v] > max(dis[u], w)) {
                dis[v] = max(dis[u], w);
                if (!inq[v]) q.push((node){v, dis[v]});
            }
        }
    }
}

int main() {
    int u, v, w;
    read(n), read(m), read(k);
    for (int i = 1; i <= m; ++i) {
        read(u), read(v), read(w);
        add(u, v, w);
        for (int j = 1; j <= k; ++j) {
            add(u + j * n, v + j * n, w);
            insert(u + (j - 1) * n, v + j * n, 0);
            insert(v + (j - 1) * n, u + j * n, 0);
        }
    }
    Dijkstra();
    if (dis[k*n+n] < INF) printf("%d", dis[k*n+n]);
    else puts("-1");
    return 0;
}