joj 1509Hamiltonian Cycle (dfs求H回路)

利用了Hamiltonian路的一些性质
#include <cstdio>
#include <memory.h>
#include <iostream>
// practice for hamilton graph and dfs.
using namespace std;
const int maxn=1000;
bool map[maxn][maxn];
int path[maxn];
bool vis[maxn];
int n , edge;
bool flag;
void dfs (int x,int cnt)//recursion with recall
{
if(cnt==(n-1))
{
if(!flag)
if(map[x][1])
{
printf("1");
for (int i=0 ; i<n-1 ; i++)
printf(" %d",path[i]);
printf(" 1\n");
flag=true;
}
return ;
}//
for (int i=1 ; i<=n ; i++)
{
if(!vis[i] && map[i][x])
{
vis[i]=1;
path[cnt]=i;
//printf("%d\t",path[cnt]);
dfs(i,cnt+1);
//printf(" %d",i);
vis[i]=0;
}
}
}
int main ()
{
char s;
int cnt;
int u;
int v;
while (scanf("%d",&n)!=EOF)
{
memset (vis , 0 , sizeof(vis));
memset (map , 0 , sizeof(map));
flag=false;
for (cnt=0 ;;cnt++)
{
getchar();
scanf("%c",&s);
if(s=='%')break;
scanf("%d",&u);
v=s-48;
//printf("%d %d",v,u);
map[v][u]=true;
map[u][v]=true;
}
edge=cnt;
if(n>2){vis[1]=1;dfs(1,0);}//begin with 0th,point1
else printf("N\n");//这里要考虑下点数小于3的情况
}
return 0;
}