1 #include 
     
       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 TreeNode23 {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 }