题干

C++实现

• 循环+双指针法(一个指向父亲，一个指向待插入结点)

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <queue>
using namespace std;struct TreeNode {char data;TreeNode* left;TreeNode* right;
};void InsertBST(TreeNode* &proot, int data) {TreeNode* pNew = new TreeNode();pNew->data = data;pNew->left = NULL;pNew->right = NULL;if (proot == NULL) {proot = pNew;printf("-1\n");}else {TreeNode* pCur = proot;//用于向下探索，插入结点TreeNode* pPre = NULL;//指向pCur的父亲while (1) {if (pCur->data > data) {pPre = pCur;pCur = pCur->left;if (pCur == NULL) {pPre->left = pNew;printf("%d\n",pPre->data);break;}}else {pPre = pCur;pCur = pCur->right;if (pCur == NULL) {pPre->right = pNew;printf("%d\n", pPre->data);break;}}}}
}int main() {int n;scanf("%d", &n);TreeNode* proot = NULL;for (int i = 0; i < n; i++){int data;scanf("%d", &data);InsertBST(proot, data);}return 0;
}