ZOJ 3965 Binary Tree Restoring

Binary Tree Restoring

思路：

递归

比较a序列和b序列中表示同一个子树的一段区间，不断递归

代码：

#include<bits/stdc++.h>
using namespace std;
#define LL long long
#define pb push_back
#define mem(a,b) memset(a,b,sizeof(a))

const int N=1e5+5;
int a[N],b[N],par[N],posa[N],posb[N],sum[N],n;
void dfs(int l,int r,int ll,int rr,int pa){
    if(l>r||ll>rr||r>n||rr>n)return ;
    if(a[l]==b[ll]){
        par[a[l]]=pa;
        sum[pa]++;
        dfs(l+1,r,ll+1,rr,a[l]);
    }
    else{
        par[a[l]]=par[b[ll]]=pa;
        sum[pa]+=2;
        int len1=posa[b[ll]]-l;
        int len2=posb[a[l]]-ll;
        dfs(l+1,l+len1-1,posb[a[l]]+1,posb[a[l]]+len1-1,a[l]);
        dfs(posa[b[ll]]+1,posa[b[ll]]+len2-1,ll+1,ll+len2-1,b[ll]);
        while(sum[pa]==2)pa=par[pa];
        dfs(l+len1+len2,r,ll+len1+len2,rr,pa);
    }
}
int main(){
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        for(int i=1;i<=n;i++)scanf("%d",&a[i]),posa[a[i]]=i;
        for(int i=1;i<=n;i++)scanf("%d",&b[i]),posb[b[i]]=i;
        mem(sum,0);
        dfs(1,n,1,n,0);
        for(int i=1;i<=n;i++)printf("%d%c",par[i]," 
"[i==n]);
    }
    return 0;
}