POJ 1201 Intervals (差分约束)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
using namespace std;
const int N = 50009;
const int M = N<<2;
int dist
;
struct LT{
    int nex,to,dis;
} L[M];
int F
,cnt;
void add(int f,int t,int d)
{
    L[cnt].dis = d;
    L[cnt].nex = F[f];
    L[cnt].to = t;
    F[f] =cnt++;
}
queue<int>que;
bool visit
;
int spfa(int st,int en)
{
    que.push(st);
    visit[st] = true;
    memset(dist,-1,sizeof(dist));
    dist[st] = 0;
    while(!que.empty()){
        int e = que.front();que.pop();
        visit[e]  = false;
        for(int i=F[e];i;i=L[i].nex){
            int to = L[i].to;
            if(dist[to]<dist[e]+L[i].dis){
                dist[to] = dist[e]+L[i].dis;
                if(!visit[to]) que.push(to),visit[to] = true;
            }
        }
    }
    return dist[en];
}
int main()
{
    freopen("in.txt","r",stdin);
    int n,r=-1;
    int a,b,c;
    scanf("%d",&n);cnt = 1;
    for(int i=0;i<n;i++)
    {
        scanf("%d%d%d",&a,&b,&c);
        if(a>b) a^=b^=a;
        add(a,b+1,c);r = max(r,b+1);
    }
    add(0,1,0);
    for(int i=1;i<r;i++)
    add(i,i+1,0),add(i,i-1,-1);
    printf("%d\n",spfa(0,r));
    return 0;
}