https://www.luogu.org/problemnew/show/P2765

題解：網(wǎng)絡(luò)流+最大流

/* *@Author: STZG *@Language: C++ */ #include <bits/stdc++.h> #include<iostream> #include<algorithm> #include<cstdlib> #include<cstring> #include<cstdio> #include<string> #include<vector> #include<bitset> #include<queue> #include<deque> #include<stack> #include<cmath> #include<list> #include<map> #include<set> //#define DEBUG #define RI register int #define endl "\n" using namespace std; typedef long long ll; //typedef __int128 lll; const int N=10000+10; const int M=100000+10; const int MOD=1e9+7; const double PI = acos(-1.0); const double EXP = 1E-8; const int INF = 0x3f3f3f3f; int s,t,n,m,k,p,l,r,u,v; int ans,cnt,flag,temp,sum,maxflow; int dis[N]; int pre[N],head[N]; bool vis[N]; struct node{int u,v;ll c;node(){};node(int u,int v,ll cap):u(u),v(v),c(cap){} }; vector<node>edge; vector<int>G[N]; int find(int x){return pre[x]==x?x:pre[x]=find(pre[x]);} void Addedge(int u,int v,ll cap){edge.push_back({u,v,cap});edge.push_back({v,u,0});int sz=edge.size();G[u].push_back(sz-2);G[v].push_back(sz-1); } bool bfs(int u){memset(dis,-1,sizeof(dis));dis[u]=0;queue<int>q;q.push(u);while(!q.empty()){int u=q.front();q.pop();for(int i=0,j=G[u].size();i<j;i++){node e=edge[G[u][i]];if(dis[e.v]<0&&e.c>0){dis[e.v]=dis[u]+1;q.push(e.v);}}}return dis[t]>0; } ll dfs(int u,ll flow){if(u==t){return flow;}ll now;for(int i=0,j=G[u].size();i<j;i++){node e=edge[G[u][i]];if(e.c>0&&dis[e.v]==dis[u]+1&&(now=dfs(e.v,min(flow,e.c)))){edge[G[u][i]].c-=now;edge[G[u][i]^1].c+=now;pre[u >> 1] = e.v >> 1;return now;}}return 0; } ll dinic(){ll res;ll maxflow=0;while(bfs(s)){while((res=dfs(s,INF))){maxflow+=res;}}return maxflow; } void init(){s=0;t=10000;edge.clear();for(int i=s;i<=t;i++)G[i].clear();ans=0;maxflow=0;memset(vis,0,sizeof(vis));memset(pre,0,sizeof(pre)); } int main() { #ifdef DEBUGfreopen("input.in", "r", stdin);//freopen("output.out", "w", stdout); #endif//ios::sync_with_stdio(false);//cin.tie(0);//cout.tie(0);//scanf("%d",&t);//while(t--){while(~scanf("%d",&n)){init();int all=0;int num=0;while(all<=n){num++;Addedge(s,num<<1,1);Addedge((num<<1)|1,t,1);for(int i=sqrt(num)+1;i*i<2*num;++i)Addedge((i*i-num)<<1,(num<<1)|1,1);if(!dinic()) head[++all]=num;}printf("%d\n",--num);for(int i = 1; i <= n; i++) {if(!vis[head[i]]) {for(int u = head[i]; u != 0 && u != (t >> 1); u = pre[u]) {vis[u] = true;printf("%d%c",u," \n"[pre[u]==0||pre[u] == (t >> 1)]);}}}}//}#ifdef DEBUGprintf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC); #endif//cout << "Hello world!" << endl;return 0; }

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