二叉树的遍历

/*
*给出中序和前序，然后构建树，之后遍历树
*/

#include <iostream>
#include <string>
#include<sstream>
#include<algorithm>
using namespace std;

const int maxv = 10000+51;
int in_order[maxv],post_order[maxv],lch[maxv],rch[maxv];
int n;

bool read_list(int *a){
        string line;
        if(!getline(cin,line))  return false;
        stringstream ss(line);
        n = 0;
        int x;
        while(ss >> x) a[n++] = x;
        return n > 0;
}

int build(int l1,int r1,int l2,int r2)
{
        if(l1>r1) return 0;
        int root = post_order[r2];
        int p = l1;
        while(in_order[p] != root) p++;
        int cnt = p - l1;
        lch[root] = build(l1,p-1,l2,l2+cnt-1);
        rch[root] = build(p+1,r1,l2+cnt,r2-1);
        return root;
}

int best,best_sum;

void dfs(int u,int sum)
{
        sum += u;
        if(!lch[u] && !rch[u])
        {
                if(sum < best_sum || (sum == best_sum && u < best ) )
                {
                        best = u;
                        best_sum = sum;
                }
        }
        if(lch[u])  dfs(lch[u],sum);
        if(rch[u])  dfs(rch[u],sum);
}


int main()
{
    while(read_list(in_order)){
        read_list(post_order);
        build(0 , n - 1 , 0 , n - 1);
        best_sum = 1000000000;
        dfs(post_order[n-1],0);
        cout<<best<<endl;
    }
    return 0;
}