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\n",spfa(s, e));

        else   printf("No solution\n");

    }

    return 0;

}