uva 548

根据中序遍历和后序遍历构建树

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <algorithm>#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 n>0;}int build(int r1,int l1,int r2,int l2){    if(r1>l1) return 0;    int root = post_order[l2];    int p = r1;    while(in_order[p]!=root) p++;    int cnt = p-r1;    lch[root] = build(r1,p-1,r2,r2+cnt-1);    rch[root] = build(p+1,l1,r2+cnt,l2-1);    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)){        //memset(lch,0,sizeof(lch));        //memset(rch,0,sizeof(rch));        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; }