loj2308 「APIO2017」商旅

ref

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
typedef long long ll;
int n, m, k, uu, vv, hea[105], cnt, tot[105];
ll b[105][1005], s[105][1005], w[105][105], bst[105][105], dis[105], ww;
bool ins[105];
const ll oo=0x3f3f3f3f3f3f3f3f;
queue<int> d;
struct Edge{
	int too, nxt;
	ll val;
}edge[20005];
void add_edge(int fro, int too, ll val){
	edge[++cnt].nxt = hea[fro];
	edge[cnt].too = too;
	edge[cnt].val = val;
	hea[fro] = cnt;
}
bool chk(ll lim){
	memset(hea, 0, sizeof(hea));
	memset(dis, 0, sizeof(dis));
	while(!d.empty())	d.pop();
	cnt = 0;
	for(int i=1; i<=n; i++)
		for(int j=1; j<=n; j++)
			if(bst[i][j]!=-1 && w[i][j]<oo)
				add_edge(i, j, bst[i][j]-lim*w[i][j]);
	for(int i=1; i<=n; i++){
		d.push(i);
		tot[i] = ins[i] = 1;
	}
	while(!d.empty()){
		int x=d.front();
		d.pop();
		ins[x] = false;
		for(int i=hea[x]; i; i=edge[i].nxt){
			int t=edge[i].too;
			if(dis[t]<=dis[x]+edge[i].val){//这里是大于等于，零环也合法
				tot[t] = tot[x] + 1;
				if(tot[t]>n)	return true;
				dis[t] = dis[x] + edge[i].val;
				if(!ins[t]){
					ins[t] = true;
					d.push(t);
				}
			}
		}
	}
	return false;
}
int main(){
	memset(w, 0x3f, sizeof(w));
	memset(bst, -1, sizeof(bst));
	cin>>n>>m>>k;
	for(int i=1; i<=n; i++)
		for(int j=1; j<=k; j++)
			scanf("%lld %lld", &b[i][j], &s[i][j]);
	for(int i=1; i<=n; i++)
		w[i][i] = 0;
	for(int i=1; i<=m; i++){
		scanf("%d %d %lld", &uu, &vv, &ww);
		w[uu][vv] = min(w[uu][vv], ww);
	}
	for(int l=1; l<=n; l++)
		for(int i=1; i<=n; i++)
			for(int j=1; j<=n; j++)
				w[i][j] = min(w[i][j], w[i][l]+w[l][j]); 

	ll l=0, r=0, mid, re;
	for(int i=1; i<=n; i++)
		for(int j=1; j<=n; j++){
			if(i!=j && w[i][j]<oo){
				bst[i][j] = 0;
				for(int l=1; l<=k; l++)
					if(s[j][l]!=-1 && b[i][l]!=-1)
						bst[i][j] = max(bst[i][j], s[j][l]-b[i][l]);
				r = max(r, bst[i][j]);
			}
		}
	while(l<=r){
		mid = (l + r) >> 1;
		if(chk(mid))	re = mid, l = mid + 1;
		else	r = mid - 1;
	}
	cout<<re<<endl;
	return 0;
}