POJ 3169 Layout——差分约束

裸题，差分约束推荐这篇博客http://www.cppblog.com/menjitianya/archive/2015/11/19/212292.html

#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;}