SWERC 2002 - Intervals (差分约束)

因为数组大小debug了好久...因为i+1，所以最后要返回50001

#include<vector>
#include<cstdio>
#include<iostream>
#include<cmath>
#include<queue>
#include<cstdlib>
#include<cstring>
#define numm ch-48
#define pd putchar(' ')
#define pn putchar('\n')
#define pb push_back
#define fi first
#define se second
#define fre1 freopen("1.txt","r",stdin)
#define fre2 freopen("2.txt","w",stdout)
using namespace std;
template <typename T>
void read(T &res) {
    bool flag=false;char ch;
    while(!isdigit(ch=getchar())) (ch=='-')&&(flag=true);
    for(res=numm;isdigit(ch=getchar());res=(res<<1)+(res<<3)+numm);
    flag&&(res=-res);
}
template <typename T>
void write(T x) {
    if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
const int maxm=8000010;
const int maxn=50005;
const int inf=0x3f3f3f3f;
const int INF=0x7fffffff;
typedef long long ll;
bool vis[maxn];
struct node {
    int to,net,w;
}e[maxn*3];
int cnt,dis[maxn],head[maxn];
queue<int>que;
void add(int u,int v,int w) {
    e[cnt].to=v;
    e[cnt].w=w;
    e[cnt].net=head[u];
    head[u]=cnt++;
}
int spfa() {
    memset(dis,192,sizeof(dis));
    dis[0]=0;
    que.push(0);
    vis[0]=true;
    while(!que.empty()) {
        int k=que.front();
        que.pop();
        vis[k]=false;
        for(int i=head[k];i!=-1;i=e[i].net) {
            int v=e[i].to;
            if(dis[k]+e[i].w>dis[v]) {
                dis[v]=dis[k]+e[i].w;
                if(!vis[v]) {
                    que.push(v);
                    vis[v]=true;
                }
            }
        }
    }
    return dis[50001];
}
int main()
{
    memset(head,-1,sizeof(head));
    int m;
    for(int i=0;i<=50000;i++)
        add(i,i+1,0),add(i+1,i,-1);
    read(m);
    for(int i=1;i<=m;i++) {
        int u,v,w;
        read(u),read(v),read(w);
        add(u,v+1,w);
    }
    write(spfa());pn;
    return 0;
}
///差分约束:
//1.t[i+1]-t[i]>=0    ->i到i+1建0边
//2.t[i]-t[i+1]>=-1   ->i+1到i建-1边
//3.t[b+1]-t[a]>=c    ->a到b+1建C边