【邻接表+匈牙利算法模板】Elementary Math

http://acm.bnu.edu.cn/v3/external/gym/101485.pdf

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int maxn=;
 struct node
 {
     ll x;
     ll y;
     int id;
 }a[maxn];
 int n;
 ll b[maxn*];
 int cnt;
 struct Edge
 {
     int to;
     int nxt;
     int w;
 }e[maxn*];
 int tot;
 int head[maxn];
 map<ll,int> mp;
 bool vis[maxn*];
 int used[maxn*];
 char op[maxn];
 void init()
 {
     tot=;
     memset(head,-,sizeof(head));
     memset(vis,false,sizeof(vis));
     memset(used,-,sizeof(used));
 }
 void add(int u,int v)
 {
     e[tot].to=v;
     e[tot].w=;
     e[tot].nxt=head[u];
     head[u]=tot++;
 }
 int dfs(int u)
 {
     for(int i=head[u];i!=-;i=e[i].nxt)
     {
         int v=e[i].to;
         if(!vis[v]&&e[i].w)
         {
             vis[v]=true;
             if(used[v]==-||dfs(used[v]))
             {
                 used[v]=u;
                 return ;
             }
         }
     }
     return ;
 }

 void output()
 {
     for(int i=;i<cnt;i++)
     {
         if(used[mp[b[i]]]==-) continue;
         int id=used[mp[b[i]]];
         if(a[id].x+a[id].y==b[i]) op[id]='+';
         else if(a[id].x-a[id].y==b[i]) op[id]='-';
         else op[id]='*';
     }
     for(int i=;i<=n;i++)
     {
         printf("%lld %c %lld",a[i].x,op[i],a[i].y);
         ll res;
         if(op[i]=='+') res=a[i].x+a[i].y;
         else if(op[i]=='-') res=a[i].x-a[i].y;
         else if(op[i]=='*') res=a[i].x*a[i].y;
         printf(" = %lld\n",res);
     }
 }
 int main()
 {
     while(~scanf("%d",&n))
     {
         init();
         mp.clear();
         cnt=;
         for(int i=;i<=n;i++)
         {
             scanf("%lld%lld",&a[i].x,&a[i].y);
             a[i].id=i;
             b[cnt++]=a[i].x+a[i].y;
             b[cnt++]=a[i].x-a[i].y;
             b[cnt++]=a[i].x*a[i].y;
         }
         sort(b,b+cnt);
         cnt=unique(b,b+cnt)-b;
 //        for(int i=0;i<cnt;i++)
 //        {
 //            cout<<b[i]<<" ";
 //        }
 //        cout<<endl;
         for(int i=;i<cnt;i++)
         {
             mp[b[i]]=i+;
         }
         for(int i=;i<=n;i++)
         {
             ll x=a[i].x+a[i].y;
             ll y=a[i].x-a[i].y;
             ll z=a[i].x*a[i].y;
             int posx=mp[x];
             int posy=mp[y];
             int posz=mp[z];
         //    cout<<posx<<" "<<posy<<" "<<posz<<endl;
             add(i,posx);
             if(posy!=posx) add(i,posy);
             if(posz!=posy && posz!=posx)    add(i,posz);
         }
         int ans=;
         for(int i=;i<=n;i++)
         {
             memset(vis,false,sizeof(vis));
             ans+=dfs(i);
         }
         if(ans<n)
         {
             puts("impossible");
         }
         else
         {
             output();
         }
     }
     return ;
 }