poj2255树的重建问题

#include<iostream> #include<cstring> #include<cstdlib> #include<cstdio> #include<string> #include<sstream> #include<vector> using namespace std; const int maxn = 30; struct node { int left; int right; char value; node() { left = -1; right = -1; } }; string pre, in; node tree[maxn]; int root = 0; int cnt = 0; vector<char> ans; int index = 0; int build(int l,int r) { if (l > r)return -1; char ch = pre[cnt++]; int pos = 0; for (int i = l; i <= r; i++) { if (in[i] == ch) { pos = i; break; } } tree[index].value = ch; tree[index].left = build(l, pos - 1); tree[index].right = build(pos + 1, r); ans.push_back(ch); return index++; } int main() { //freopen("input.txt","r",stdin); while (cin >> pre) { cin >> in; root = 0; cnt = 0; index = 0; for (int i = 0; i < maxn; i++)tree[i].left = -1, tree[i].right = -1; ans.clear(); root = build(0, pre.length()-1); for (int i = 0; i < ans.size(); i++) cout << ans[i]; cout << endl; } return 0; }