POJ 3169 Layout——差分约束

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#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <queue>
using namespace std;
const int MAXN = 1010;
const int MAXM = 200010;
const int INF = 0x3f3f3f3f;
bool vis[MAXN];
int N, ML, MD, tot, head[MAXN], num[MAXN], dis[MAXN];
struct Edge {
    int to, cost, next;
}edge[MAXM];
void Init() {
    tot = 0;
    for (int i = 1; i <= N; i++) head[i] = -1;
}

void AddEdge(int u, int v, int cost) {
    tot++;
    edge[tot].to = v;
    edge[tot].cost = cost;
    edge[tot].next = head[u];
    head[u] = tot;
}

int spfa() {
    for (int i = 1; i <= N; i++) dis[i] = INF, vis[i] = false, num[i] = 0;
    dis[1] = 0, num[1]++;
    queue<int> q; q.push(1);
    while (!q.empty()) {
        int u = q.front(); q.pop();
        vis[u] =false;
        for (int i = head[u]; i != -1; i = edge[i].next) {
            int v = edge[i].to, cost = edge[i].cost;
            if (dis[v] > dis[u] + cost) {
                dis[v] = dis[u] + cost;
                if (!vis[v]) {
                    vis[v] = true;
                    num[v]++;
                    q.push(v);
                    if (num[v] > N) {
                        return -1;
                    }
                }
            }
        }
    }
    return dis[N] == INF ? -2 : dis[N];
}

int main() {
    while (~scanf("%d %d %d", &N, &ML, &MD)) {
        Init();
        for (int i = 1; i <= ML; i++) {
            int u, v, cost; scanf("%d %d %d", &u, &v, &cost);
            AddEdge(u, v, cost);
        }
        for (int i = 1; i <= MD; i++) {
            int u, v, cost; scanf("%d %d %d", &u, &v, &cost);
            AddEdge(v, u, -cost);
        }
        printf("%d\n", spfa());
    }
    return 0;
}