HDU 5424 backtracking + and check-set to determine connectivity

Test instructions: A graph of N-point n points is given to determine if there is a Hamiltonian path.

Idea: First use and check the set to determine whether the diagram is connected, and then from the smallest point of the degree of backtracking, to see if a Hamiltonian path can be found.

1#include <iostream>2#include <cstring>3#include <cstdio>4#include <Set>5 using namespacestd;6 7 Const intINF =999999;8 Const intN =1001;9 intF[n];Ten intD[n]; One intHead[n]; A BOOLVisit[n]; - intN, E; -  the voidInit () - { -E =0; -memset (D,0,sizeof(d)); +Memset (Head,-1,sizeof(head)); -memset (Visit,0,sizeof(visit)); +      for(inti =1; i < N; i++) F[i] =i; A } at  - structEdge - { -     intV, next; -} edge[n <<1]; -  in voidAddedge (intUintv) - { toEDGE[E].V =v; +Edge[e].next =Head[u]; -Head[u] = e++; the } *  $ intFINDF (intx)Panax Notoginseng { -     if(f[x]! = x) F[x] =findf (f[x]); the     returnF[x]; + } A  the BOOLUnion_set (intXinty) + { -x = FINDF (x), y =findf (y); $     if(x = =y) $     { -         return false; -     } the     Else -     {WuyiF[X] =y; the         return true; -     } Wu } -  About BOOLDfsintUintCNT) $ { -     if(cnt = = N)return true; -      for(inti = Head[u]; I! =-1; i =edge[i].next) -     { A         intv =edge[i].v; +         if( !Visit[v]) the         { -VISIT[V] =1; $             if(Dfs (V, CNT +1) )return true; theVISIT[V] =0; the         } the     } the     return false; - } in  the intMain () the { About      while(SCANF ("%d", &n)! =EOF) the     { the init (); the         intc =0; +          for(inti =1; I <= N; i++ ) -         { the             intu, v;Bayiscanf"%d%d", &u, &v); the Addedge (U, v); the Addedge (V, u); -d[u]++, d[v]++; -             if(Union_set (U, v)) C + +; the         } the         if(c! = N-1 ) the         { thePuts"NO"); -             Continue; the         } thed[0] =INF;  the         intK =0;94          for(inti =1; I <= N; i++ ) the         { the             if(D[i] <D[k]) the             {98K =i; About             } -         } 101VISIT[K] =1;102         if(Dfs (k,1 ) )103         {104Puts"YES"); the         }106         Else107         {108Puts"NO");109         } the     }111     return 0; the}

HDU 5424 backtracking + and check-set to determine connectivity