TREE UVA 548

题目：先给一组中序遍历和一组后序遍历，再在叶子中找一个使其到根的路径的权和最小（相等取叶子小的），输出权和。

#include <bits/stdc++.h>
using namespace std;
const int maxv = 10000+10;
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 = 100000000;
            //书上好像没有设置best的初始值。
            best = 10000000;
            dfs(post_order[n-1],0);
            cout<<best<<endl;

        }
        return 0;}