Ural 1450 求最长路 SPFA

题意就是求S点到T点的有向无环图中的最长路。

用SPFA可以解决。

一开始一直RE的原因 QAQ

竟然是在开Edge 邻接表的时候开小了

改了一下4Y

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <iostream>
#include <stack>
#include <queue>
#include <algorithm>

#define ll long long
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAXN = 124799;
const int MAXSIZE = 1002;

int dis[MAXSIZE],head[MAXSIZE],vis[MAXSIZE];
int n, cnt;

struct node{
      int u,v,val,next;
} Edge[MAXN];

void addEdge(int u,int v,int val){
      Edge[cnt].u=u;
      Edge[cnt].v=v;
      Edge[cnt].val=val;
      Edge[cnt].next=head[u];
      head[u]=cnt++;
}

void init(){
    memset(head, -1, sizeof(head));
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; ++i) dis[i] = -INF;
    cnt = 0;
}

int spfa(int src, int ter){
    queue<int>q;
    q.push(src);
    vis[src]=1;
    dis[src]=0;
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=head[u]; i!=-1; i=Edge[i].next){
            int v=Edge[i].v;
            if(dis[v]<dis[u]+Edge[i].val){
                dis[v]=dis[u]+Edge[i].val;
                if(!vis[v]){
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
    return dis[ter];
}

int main(){
    int i, j, k, t, numCase;
    int ss, ee, val;
    int s, e;
    while(EOF != scanf("%d%d",&n,&numCase)){
        init();
        while(numCase--){
            scanf("%d%d%d",&ss,&ee,&val);
            addEdge(ss,ee,val);
        }
        scanf("%d%d",&s,&e);
        int ans = spfa(s, e);
        if(ans > 0) printf("%d
",spfa(s, e));
        else   printf("No solution
");
    }
    return 0;
}