CodeVS 1242 布局

//差分约束系统//以x-y <= k为例，等价于x <= k+y，相当于x和y之间的连边最大权值为k，然后跑最短路即知最大解。 //好久不做CodeVS了，洛谷大法好！#include<bits/stdc++.h>using namespace std;const int inf = 0x3f3f3f3f;queue<int> q;int n, m1, m2, tot;bool flag = 0, vis[1010];int dis[1010], st[1010], got[1010];struct node{    int v, w, nxt;} edge[20010];inline void in(int x, int y, int z){    edge[++tot].v = y;    edge[tot].w = z;    edge[tot].nxt = st[x];    st[x] = tot;}inline void getInit(){    memset(vis, 0, sizeof(0));    for(int i = 0; i <= n; i++)        dis[i] = inf;}inline void GoSPFA(){    q.push(1);    vis[1] = 1;    dis[1] = 0;    while(!q.empty()){        int now = q.front(); q.pop();        vis[now] = 0;        for(int i = st[now]; i; i = edge[i].nxt){            int to = edge[i].v;            if(dis[to] > dis[now] + edge[i].w){                dis[to] = dis[now] + edge[i].w;                got[to]++;                if(got[to] >= n){                    flag = 1;                    return;                }                vis[to] = 1;                q.push(to);            }        }    }}int main(){    scanf("%d%d%d", &n, &m1, &m2);    for(int i = 1, x, y, z; i <= m1; i++){        scanf("%d%d%d", &x, &y, &z);        in(x, y, z);    }    for(int i = 1, x, y, z; i <= m2; i++){        scanf("%d%d%d", &x, &y, &z);        in(y, x, -z);    }    getInit();    GoSPFA();    if(flag)    printf("-1\n");    else if(dis[n] < inf)   printf("%d\n", dis[n]);    else printf("-2\n");    return 0;}