1 #include <bits/stdc++.h> 2 #define _for(i,a,b) for(int i = (a);i < b;i ++) 3 typedef long long ll; 4 using namespace std; 5 int N; 6 string s[30]; 7 inline ll read() 8 { 9 ll ans = 0; 10 char ch = getchar(), last = ' '; 11 while(!isdigit(ch)) last = ch, ch = getchar(); 12 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar(); 13 if(last == '-') ans = -ans; 14 return ans; 15 } 16 inline void write(ll x) 17 { 18 if(x < 0) x = -x, putchar('-'); 19 if(x >= 10) write(x / 10); 20 putchar(x % 10 + '0'); 21 } 22 struct TreeNode 23 { 24 char val; 25 TreeNode *left; 26 TreeNode *right; 27 }; 28 int go(char c) 29 { 30 _for(i,0,N) 31 if(s[i][0]==c) 32 return i; 33 return -1; 34 } 35 TreeNode* build(int cur,char give) 36 { 37 if(give=='*') 38 return NULL; 39 TreeNode* t = (TreeNode*)malloc(sizeof(TreeNode)); 40 t->val = give; 41 t->left = build(go(s[cur][1]),s[cur][1]); 42 t->right = build(go(s[cur][2]),s[cur][2]); 43 return t; 44 } 45 void preorder(TreeNode *root) 46 { 47 if(!root) 48 return ; 49 printf("%c",root->val); 50 preorder(root->left); 51 preorder(root->right); 52 } 53 int main() 54 { 55 TreeNode* root; 56 N = read(); 57 _for(i,0,N) 58 cin >> s[i]; 59 root = build(0,s[0][0]); 60 preorder(root); 61 return 0; 62 }