![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include<stdio.h> 2 #include<stdlib.h> 3 typedef struct node *btlink; 4 struct node 5 { 6 int data; 7 btlink left; 8 btlink right; 9 int t; 10 }; 11 12 btlink BT; 13 void insert(btlink q, int x) 14 { 15 btlink p = (btlink)malloc(sizeof(node)); 16 p->data = x; 17 p->left = NULL; 18 p->right = NULL; 19 p->t=0; 20 if(q == NULL) 21 { 22 BT = p; 23 //printf("BT=%d ",BT->t); 24 return ; 25 } 26 while(q->left!=p&&q->right!=p) 27 { 28 if(x<q->data) 29 { 30 if(q->left) 31 { 32 q->t++; 33 q = q->left; 34 } 35 else 36 { 37 q->t++; 38 q->left = p; 39 } 40 } 41 else 42 { 43 if(q->right) 44 { 45 q = q->right; 46 } 47 else 48 { 49 q->right = p; 50 } 51 } 52 } 53 return; 54 } 55 void InOrder(btlink root,int k) 56 { 57 58 while(k!=root->t+1) 59 { 60 //printf("k=%d t=%d ",k,root->t); 61 if(k>root->t+1) 62 { 63 k=k-root->t-1; 64 root=root->right; 65 } 66 else 67 { 68 69 root=root->left; 70 } 71 } 72 printf("%d ",root->data); 73 } 74 75 int main() 76 { 77 int n,i,index=0,x; 78 char a[8]; 79 scanf("%d",&n); 80 BT=(btlink)malloc(sizeof(node)); 81 BT=NULL; 82 for(i=0;i<n;i++) 83 { 84 scanf("%s",a); 85 if(a[0]=='a') 86 { 87 scanf("%d",&x); 88 insert(BT,x); 89 } 90 else if(a[0]=='p') 91 { 92 93 index++; 94 InOrder(BT,index); 95 } 96 } 97 return 0; 98 }