hdu1710 Binary Tree Traversals_hdu 1710 binary tree traversals-优快云博客

本文介绍了解决UVA548问题的两种方法：使用数组和指针构建二叉树，并给出了从给定的前序和中序遍历序列生成后续遍历序列的具体实现。

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是 uva548 减弱版，给一棵树的前序，中序输出后续。

两种建树的方法，数组（推荐），指针。

#include <fstream>
#include <iostream>
#include <string>
#include <cstring>
#include <complex>
#include <math.h>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <stdio.h>
#include <stack>
#include <algorithm>
#include <list>
#include <ctime>
#include <ctime>
#include <assert.h>

#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define eps 1e-8
#define M_PI 3.141592653589793

typedef long long ll;
const ll mod=1000000007;
const int inf=0x7fffffff;
ll powmod(ll a,ll b) {ll res=1;a%=mod;for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
using namespace std;
const int maxn=1000+10;

int pre_order[maxn],in_order[maxn],l[maxn],r[maxn],ok;

int bulid(int l1,int r1,int l2,int r2)
{
     if(l2>r2) return 0;
     int root=pre_order[l1];
     int p=l2;
     while(in_order[p]!=root) p++;
     int cnt=p-l2;
     l[root]=bulid(l1+1,l1+cnt,l2,p-1);
     r[root]=bulid(l1+cnt+1,r1,p+1,r2);
     return root;
}

void post_order(int root)
{
    if(l[root]!=0)  post_order(l[root]);
    if(r[root]!=0) post_order(r[root]);
    if(!ok) ok=1;
    else printf(" ");
    printf("%d",root);
}

int main()
{
   int n;
   while(~scanf("%d",&n)){
      memset(l,0,sizeof(l));
      memset(r,0,sizeof(r));
      for(int i=1;i<=n;i++) scanf("%d",&pre_order[i]);
      for(int i=1;i<=n;i++) scanf("%d",&in_order[i]);
      bulid(1,n,1,n);
      ok=0;
      post_order(pre_order[1]);
      printf("\n");
   }
}

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
struct Node{
   int v;
   Node *left,*right;
};
Node *root;
Node *newnode() {return new Node();}
const int maxn=2000+10;
int pre_order[maxn],in_order[maxn],n,ok;

int Find(int *a,int s,int e,int v)
{
    for(int i=s;i<=e;i++)
      if(a[i]==v) return i;
    return 0;
}
Node* bulid(int l1,int r1,int l2,int r2)
{
   if(l2>r2) return NULL;
   int p=l2;
   while(in_order[p]!=pre_order[l1]) p++;
   int cnt=p-l2;
   Node *t=newnode();
   t->v=pre_order[l1];
   t->right=bulid(l1+cnt+1,r1,p+1,r2);
   t->left=bulid(l1+1,l1+cnt,l2,p-1);
   return t;
}



void post_order(Node *t)
{
   if(t){
     if(t->left) post_order(t->left);
     if(t->right) post_order(t->right);
     if(ok) cout<<" ";
     else ok=1;
     cout<<t->v;
   }
   return;
}

void Delete(Node* t)
{
    if(!t->left) Delete(t->left);
    if(!t->right) Delete(t->right);
    delete t;
}

int main()
{
    while(~scanf("%d",&n)){
        ok=0;
        for(int i=1;i<=n;i++) scanf("%d",&pre_order[i]);
        for(int i=1;i<=n;i++) scanf("%d",&in_order[i]);
        root=bulid(1,n,1,n);
        post_order(root);
        cout<<endl;
        //Delete(root);
    }
}