BST的查找非常简单，插入是基于查找进行的，有一点需要注意的是插入一定是称为叶子节点的孩子节点。删除稍微麻烦一点，要分情况讨论，当要删除的节点有两个孩子节点时，首先寻找要删除节点p的左子树的最大的节点s，然后交换p和s的数值，调整s父节点的指向，删除s节点。
1 /search x on a BST,return the node's pointer 2 TreeNode* searchBST(TreeNode* root,int x){ 3 if(root == nullptr) return nullptr; 4 if(root->val == x) return root; 5 if(x > root->val) return searchBST(root->right,x); 6 if(x < root->val) return searchBST(root->left,x); 7 return nullptr; 8 } 9 10 TreeNode* searchBST2(TreeNode* root,int x){ 11 TreeNode* p = root; 12 while(p){ 13 if(x == p->val) return p; 14 else if(x > p->val) { 15 p = p->right; 16 }else{ 17 p = p->left; 18 } 19 } 20 return nullptr; 21 } 22 23 //if bst has x return false,else insert and return true; 24 bool insertBST(TreeNode* root,int x){ 25 TreeNode* p = root; 26 TreeNode* pre = nullptr; 27 while(p){ 28 if(x == p->val){ 29 return false; 30 }else if(x > p->val){ 31 pre = p; 32 p = p->right; 33 }else{ 34 pre = p; 35 p = p->left; 36 } 37 } 38 TreeNode* px = new TreeNode(x); 39 if(pre == nullptr){ 40 root = px; 41 }else if(x < pre->val){ 42 pre->left = px; 43 }else{ 44 pre->right = px; 45 } 46 return true; 47 } 48 49 50 void removerBST(TreeNode* root,int x){ 51 if(root == nullptr) return; 52 TreeNode* p = root; 53 TreeNode* pp = nullptr; 54 while(p){ 55 if(p->val == x){{ 56 break; 57 } 58 }else if(x > p->val){ 59 pp = p; 60 p = p->right; 61 }else{ 62 pp = p; 63 p = p->left; 64 } 65 } 66 67 if(p == nullptr) return; //not found! 68 69 //when p has two child 70 if(p->left && p->right){ 71 TreeNode* s = p->left; 72 TreeNode* ps = p; 73 while(s->right){ 74 ps = s; 75 s = s->right; 76 } 77 std::swap(p->val,s->val); 78 if(s == ps->right) ps->right = s->left; 79 else if(s == ps->left) ps->left = s->left; 80 delete s; 81 return; 82 } 83 84 //when p has one or zero child 85 TreeNode* c = nullptr; 86 if(p->left) c = p->left; 87 if(p->right) c = p->right; 88 if(p==root){ 89 root = c; 90 }else{ 91 if(p == pp->left){ 92 pp->left = c; 93 }else{ 94 pp->right = c; 95 } 96 delete p; 97 } 98 99 }