树，UVA 548

#include<iostream>#include<string>#include<sstream>#include<algorithm>using namespace std;const int maxv = 1000 + 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;}///把in_order[L1...R1]和post_order[L2...R2]建成一棵二叉树，返回树根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; ///左子树结点个数    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; ///目前为止的最优解和对应的和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(void){    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 << "\n";    }    return 0;}