uva 548 Tree

#include<iostream>#include<cstdio>#include<sstream>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 true;}int buildtree(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 len=p-L1;    lch[root]=buildtree(L1,p-1,L2,L2+len-1);    rch[root]=buildtree(p+1,R1,L2+len,R2-1);    return root;}int best_sum=10000000,best;void dfs(int u,int sum){    sum+=u;    if(!lch[u]&&!rch[u]) {        if(best_sum>sum||(best_sum==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);        buildtree(0,n-1,0,n-1);        int u=post_order[n-1];        best_sum=1000000;        dfs(u,0);        cout<<best<<endl;    }    return 0;}