BST的INSERT、FIND、DELETE、遍历

        嗯...就是贴个板子

#include <bits/stdc++.h>
using namespace std;
struct node{
	int num;
	node *p, *l, *r;
};
node *root, *null;
int n, xx;
string str;

void p_inorder(node *x){     // 中序遍历
	if(x == null) return ;
	p_inorder(x -> l);
	printf(" %d", x -> num);
	p_inorder(x -> r);
	return ;
}

void p_preorder(node *x){    // 前序遍历
	if(x == null) return ;
	printf(" %d", x -> num);
	p_preorder(x -> l);
	p_preorder(x -> r);
	return ;
}

bool find(int a){           // 查询
	node *x = root;
	while(x != null){
		if(x -> num == a) return true;
		if(a > x -> num) x = x -> r;
		else x = x -> l;
	}
	return false;
}

void insert(int a){          // 插入
	node *x = root, *y = null;
	node *z = new node();
	z -> num = a;
	z -> l = null; z -> r = null;
	while(x != null){
		y = x;
		if(z -> num < x -> num) x = x -> l;
		else x = x -> r;
	}
	z -> p = y;
	if(y == null) root = z;
	else{
		if(z -> num < y -> num) y -> l = z;
		else y -> r = z;
	}
	return ;
}

void del(int x){
  node *p = root , *par;
  while(p -> num != x){
    if(p -> num > x){
      par = p;
      p = p -> l;
    }
    else{
      par = p;
      p = p -> r;
    }
  }
  if(p -> l == null && p -> r == null){
    if(par -> l == p) par -> l = null;
    else if(par -> r == p) par -> r = null;
    delete p;
    return ;
  }
  if(p -> l != null && p -> r == null){
    if(p == root) root = p -> l;
    else if(par -> l == p) par -> l = p -> l;
    else if(par -> r == p) par -> r = p -> l;
    delete p;
    return ;
  }
  else if(p -> l == null && p -> r != null){
    if(p == root) root = p -> r;
    else if(par -> l == p) par -> l = p -> r;
    else if(par -> r == p) par -> r = p -> r;
    delete p;
    return ;
  }
  else if(p -> l != null && p -> r != null){
    node *left = p -> r;
    par = p;
    while(left -> l){
      par = left;
      left = left -> l;
    }
    p -> num = left -> num;
    if(par -> l == left) par -> l = left -> r;
    else if(par -> r == left) par -> r = left -> r;
    delete left;
    return ;
  }
}

int main()
{
	scanf("%d", &n);
	for(int i=0;i<n;i++){
		cin>>str;
		if(str == "insert"){
			scanf("%d", &xx);
			insert(xx);
		}
		else if(str == "find"){
			scanf("%d", &xx);
			if(find(xx)) puts("yes");
			else puts("no");
		}
    else if(str == "delete"){
      scanf("%d", &xx);
      del(xx);
    }
		else{
			p_inorder(root);
			puts("");
			p_preorder(root);
			puts("");
		}
	}
	return 0;
}