bzoj1149

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1149

水题。。。。。

直接BFS。

#include<cstdio>

#include<cstdlib>

#include<iostream>

#include<fstream>

#include<algorithm>

#include<cstring>

#include<string>

#include<cmath>

#include<queue>

#include<stack>

#include<map>

#include<utility>

#include<set>

#include<bitset>

#include<vector>

#include<functional>

#include<deque>

#include<cctype>

#include<climits>

#include<complex>

//#include<bits/stdc++.h>适用于CF,UOJ，但不适用于poj

 

using namespace std;



typedef long long LL;

typedef double DB;

typedef pair<int,int> PII;

typedef complex<DB> CP;



#define mmst(a,v) memset(a,v,sizeof(a))

#define mmcy(a,b) memcpy(a,b,sizeof(a))

#define re(i,a,b)  for(i=a;i<=b;i++)

#define red(i,a,b) for(i=a;i>=b;i--)

#define fi first

#define se second

#define m_p(a,b) make_pair(a,b)

#define SF scanf

#define PF printf

#define two(k) (1<<(k))



template<class T>inline T sqr(T x){return x*x;}

template<class T>inline void upmin(T &t,T tmp){if(t>tmp)t=tmp;}

template<class T>inline void upmax(T &t,T tmp){if(t<tmp)t=tmp;}



const DB EPS=1e-9;

inline int sgn(DB x){if(abs(x)<EPS)return 0;return(x>0)?1:-1;}

const DB Pi=acos(-1.0);



inline int gint()

  {

        int res=0;bool neg=0;char z;

        for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar());

        if(z==EOF)return 0;

        if(z=='-'){neg=1;z=getchar();}

        for(;z!=EOF && isdigit(z);res=res*10+z-'0',z=getchar());

        return (neg)?-res:res; 

    }

inline LL gll()

  {

      LL res=0;bool neg=0;char z;

        for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar());

        if(z==EOF)return 0;

        if(z=='-'){neg=1;z=getchar();}

        for(;z!=EOF && isdigit(z);res=res*10+z-'0',z=getchar());

        return (neg)?-res:res; 

  }



const int maxN=100000;



int N;

PII a[maxN+100];

int maxdep,dep[maxN+100];

int ans;

int head,tail,que[maxN+100];

int cnt,val[2*maxN+100],sum[2*maxN+100];



int main()

  {

      freopen("bzoj1149.in","r",stdin);

      freopen("bzoj1149.out","w",stdout);

      int i;

      N=gint();

      dep[1]=1;

      re(i,1,N)

        {

            a[i].fi=gint(),a[i].se=gint();

            if(a[i].fi!=-1)dep[a[i].fi]=dep[i]+1;

            if(a[i].se!=-1)dep[a[i].se]=dep[i]+1;

        }

        ans=0;

        re(i,1,N)upmax(maxdep,dep[i]);

      re(i,1,N)if(a[i].fi==-1 || a[i].se==-1)if(maxdep-dep[i]>1){ans=-1;break;}

      if(ans==-1){cout<<ans<<endl;return 0;}

      que[head=tail=1]=1;

      re(i,2,maxdep-1)

        {

            int temp=tail;

            while(head<=temp)

              {

                  int u=que[head++];

                  que[++tail]=a[u].fi;

                  que[++tail]=a[u].se;

              }

        }

      re(i,head,tail)

        {

            int u=que[i];

            val[++cnt]=(a[u].fi==-1)?0:1;

            val[++cnt]=(a[u].se==-1)?0:1;

        }

      re(i,1,N)sum[i]=sum[i-1]+val[i];

      int l=1,r=cnt;

      while(l<r)

        {

            int mid=(l+r)/2;

            int lf,rf;

            if(sum[mid]-sum[l-1]==mid-l+1) lf=1; else if(sum[mid]-sum[l-1]==0) lf=0; else lf=2;

            if(sum[r]-sum[mid]==r-mid) rf=1; else if(sum[r]-sum[mid]==0) rf=0; else rf=2;

            if(lf==2 && rf==2) {ans=-1;break;}

            if(lf==1 && rf==0) break;

            if(lf==0 && rf==1) {ans++;break;}

            if(lf==0 && rf==0) break;

            if(lf==1 && rf==1) break;

            if(lf==0 && rf==2) {ans++;l=mid+1;continue;}

            if(lf==1 && rf==2) {l=mid+1;continue;}

            if(lf==2 && rf==0) {r=mid;continue;}

            if(lf==2 && rf==1) {ans++;r=mid;continue;}

        }

      cout<<ans<<endl;

      return 0;

  }

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