zoj 3805 Machine

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=5337

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;

vector<int>g[1001100];
int a[100101];
int in[100101];
int n;
int dfs(int u)
{
    int c,x;
    if(in[u]==0) return 1;
    if(in[u]==1)
    {
        c=dfs(g[u][0]);
        return c;
    }
    else
    {
        c=dfs(g[u][0]);
        x=dfs(g[u][1]);
        if(c!=x) return max(x,c);
        else return c+1;
    }

}

int main()
{
   while(scanf("%d",&n)!=EOF)
   {
       for(int i=1; i<=n; i++)
       {
           g[i].clear();
       }
       memset(in,0,sizeof(in));
       for(int i=1; i<=n-1; i++)
       {
           scanf("%d",&a[i]);
           g[a[i]].push_back(i+1);
           in[a[i]]++;
       }
       printf("%d
",dfs(1));
   }
   return 0;
}