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  • 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;
    }
    
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  • 原文地址:https://www.cnblogs.com/poorpool/p/9006365.html
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