SXCPC2018 nucoj1999 占领城市

#include <iostream>

#include <cstring>

#include <cstdio>

#include <queue>

using namespace std;

int n, m, e, a[305], w[305][305], uu, vv, ww, hea[805], cnt, ss, tt, maxFlow;

int lev[805], cur[805];

const int oo=0x3f3f3f3f;

queue<int> d;

struct Edge{

	int too, nxt, val;

}edge[200005];

void add_edge(int fro, int too, int val){

	edge[cnt].nxt = hea[fro];

	edge[cnt].too = too;

	edge[cnt].val = val;

	hea[fro] = cnt++;

}

void addEdge(int fro, int too, int val){

	add_edge(fro, too, val);

	add_edge(too, fro, 0);

}

bool bfs(){

	memset(lev, 0, sizeof(lev));

	lev[ss] = 1;

	d.push(ss);

	while(!d.empty()){

		int x=d.front();

		d.pop();

		for(int i=hea[x]; i!=-1; i=edge[i].nxt){

			int t=edge[i].too;

			if(!lev[t] && edge[i].val>0){

				lev[t] = lev[x] + 1;

				d.push(t);

			}

		}

	}

	return lev[tt]!=0;

}

int dfs(int x, int lim){

    if(x==tt)   return lim;

    int addFlow=0;

    for(int &i=cur[x]; i!=-1; i=edge[i].nxt){

        int t=edge[i].too;

        if(lev[t]==lev[x]+1 && edge[i].val>0){

            int tmp=dfs(t, min(lim-addFlow, edge[i].val));

            edge[i].val -= tmp;

            edge[i^1].val += tmp;

            addFlow += tmp;

            if(addFlow==lim)    break;

        }

    }

    return addFlow;

}

void dinic(){

	while(bfs()){

		for(int i=ss; i<=tt; i++)

			cur[i] = hea[i];

		maxFlow += dfs(ss, oo);

	}

}

bool chk(int lim){

	memset(hea, -1, sizeof(hea));

	ss = 0; tt = n + m + 1;

	cnt = 0;

	for(int i=1; i<=n; i++){

		addEdge(ss, i, 1);

		for(int j=1; j<=m; j++)

			if(w[a[i]][j]<=lim)

				addEdge(i, n+j, 1);

	}

	for(int i=1; i<=m; i++)

		addEdge(n+i, tt, 1);

	maxFlow = 0;

	dinic();

	if(maxFlow!=min(n,m))	return false;

	return true;

}

int main(){

	cin>>n>>m>>e;

	memset(w, 0x3f, sizeof(w));

	for(int i=1; i<=n; i++)

		scanf("%d", &a[i]);

	for(int i=1; i<=m; i++)

		w[i][i] = 0;

	for(int i=1; i<=e; i++){

		scanf("%d %d %d", &uu, &vv, &ww);

		w[uu][vv] = w[vv][uu] = min(w[uu][vv], ww);

	}

	for(int k=1; k<=m; k++)

		for(int i=1; i<=m; i++)

			for(int j=1; j<=m; j++)

				w[i][j] = min(w[i][j], w[i][k]+w[k][j]);

	int l=0, r=258262, mid, re;

	while(l<=r){

		mid = (l + r) >> 1;

		if(chk(mid))	re = mid, r = mid - 1;

		else	l = mid + 1;

	}

	cout<<re<<endl;

	return 0;

}
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SXCPC2018 nucoj1999 占领城市

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