差分约束Poj3159 Candies

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#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <algorithm>

#include <cmath>

#include <stack>

#include <queue>

#include <vector>

#include <map>

#include <string>

#include <iostream>

int
n;

using
namespace std;

struct
edge

{

    int
to;int
val;int
next;

}e[555555];

int
len;int
head[33333];

void
add(int
from ,int
to,int
val)

{

    e[len].to=to;e[len].val=val;

    e[len].next=head[from];head[from]=len++;

}

const
int INF=0xfffffff;

int
dis[44444];

void
spfa(int
x)

{

    int
vis[444444];

    for(int
i=1;i<=n;i++) vis[i]=0;

    for(int
i=1;i<=n;i++) dis[i]=INF;

    dis[x]=0; vis[x]=1;

    stack<int> q;// 不知道为什么 栈能过  队列却不行。

    q.push(x);

    while(!q.empty()){

        int
cur=q.top();vis[cur]=0;q.pop();

        for(int
i= head[cur];i!=-1;i=e[i].next){

            int
cc=e[i].to;

            if(dis[cc]>dis[cur]+e[i].val){

                dis[cc]=dis[cur]+e[i].val;

                if(!vis[cc]){

                    vis[cc]=1;

                    q.push(cc);

                }

            }

        }

    }

}

int
main()

{

    int
m;

    scanf("%d%d",&n,&m);

        len=0;memset(head,-1,sizeof(head));

        for(int
i=0;i<m;i++){

            int
a,c,b;

            scanf("%d%d%d",&a,&b,&c);

            add(a,b,c);

        }

        spfa(1);

        printf("%d\n",dis[n]);

    return
0;

}