uva548 - Tree 入门经典II 第六章数据结构基础 例题6-8

题目链接：http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=489

已知中序遍历、后序遍历，找一个叶子使它到根的路径上权和最小，输出这个叶子。

#include<stdio.h>#include<iostream>#include<string>#include<sstream>using namespace std;const int maxn = 10000 + 10;int n;int in_order[maxn],post_order[maxn],lch[maxn],rch[maxn];bool read_list(int *a){    string line;    if(!getline(cin,line)) return false;    stringstream ss(line);    int x;    n=0;    while(ss >> x) a[n++]=x;    return true;}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=2147483647;        dfs(post_order[n-1],0);        cout << best << endl;    }    return 0;}