POJ 1201 Intervals[差分約束]

時間 2019-11-19

標籤 poj intervals 差分約束简体版

原文原文鏈接

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
#define N 1000005
#define INF 999999999
int head[N], vis[N], queue[N], dis[N], outqueue[N];
int n, index;

struct Edge
{
    int v, value, next;
}edge[N];
void add_Edge(int u, int v, int val)
{
    edge[index].next=head[u];
    edge[index].v=v;
    edge[index].value=val;
    head[u]=index++;
}

void Spfa(int s)
{
    int iq=0, front=0, i, top;
    memset(vis, 0, sizeof(vis));
    memset(outqueue, 0, sizeof(outqueue));
    for(i=1; i<=n; i++)
        dis[i]=INF;
    dis[s]=0;
    queue[iq++]=s;
    vis[s]=1;
    while(iq!=front)
    {
        top=queue[front];
        front++;
        vis[top]=0;
        outqueue[top]++;
        if(outqueue[top]>n)  return ;
        for(i=head[top]; i!=-1; i=edge[i].next)
        {
            if(dis[top]+edge[i].value<dis[edge[i].v])
            {
                dis[edge[i].v]=dis[top]+edge[i].value;
                if(vis[edge[i].v]==0)
                {
                    vis[edge[i].v]=1;
                    queue[iq++]=edge[i].v;
                }
            }
        }
    }
}
int main()
{
    int nn, a, b, c, i, maxn;
    while(scanf("%d", &n)!=EOF)
    {
        maxn=0, index=0;
        memset(head, -1, sizeof(head));
        for(i=0; i<n; i++)
        {
            scanf("%d%d%d", &a, &b, &c);
            maxn=max(maxn, b);
            add_Edge(a-1, b, -1*c);
        }
        for(i=1; i<=maxn; i++)
        {
            add_Edge(i, i-1, 1);
            add_Edge(i-1, i, 0);
        }
        n=maxn;
        Spfa(0);
        printf("%d\n", -1*dis[maxn]);
    }
    return 0;
}