C++ 解法, 执行用时: 2ms, 内存消耗: 404KB, 提交时间: 2020-11-01

#include<bits/stdc++.h>
using namespace std;
struct BinaryTree{
    int data;
    BinaryTree *lchild,*rchild;
    BinaryTree(int data):data(data),lchild(NULL),rchild(NULL){}
};
void fun(BinaryTree *root,vector<int> &vec){
    if(root){
        fun(root->lchild,vec);
        vec.push_back(root->data);
        fun(root->rchild,vec);
    }
}
int main()
{
    int x;
    cin>>x;
    BinaryTree *root=new BinaryTree(x);
    map<int,BinaryTree*> mapp;
    mapp[x]=root;
    int a,b,c;
    while(scanf("%d:%d|%d",&a,&b,&c)!=EOF){
        if(mapp.find(a)!=mapp.end()){
            BinaryTree *temp=mapp[a];
            if(b!=-1){
                temp->lchild=new BinaryTree(b);
                mapp[b]=temp->lchild;
            }
            if(c!=-1){
                temp->rchild=new BinaryTree(c);
                mapp[c]=temp->rchild;
            }
        }
    }
    vector<int> vec;
    fun(root,vec);
    for(int i=1;i<vec.size();i++){
        if(vec[i-1]>vec[i]){
            cout<<"0";
            return 0;
        }
    }
    cout<<"1";
    return 0;
}

C++ 解法, 执行用时: 2ms, 内存消耗: 424KB, 提交时间: 2021-09-15

#include <bits/stdc++.h>
using namespace std;

vector<int> v;
int res = 1;
struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode() {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

void dfs(TreeNode* node) {
    if (node == nullptr) return;
    dfs(node->left);
    if (!v.empty()) {
        if (v[v.size() - 1] > node->val) {
            res = 0;
            return;
        }
    }
    v.push_back(node->val);
    dfs(node->right);
}

int isBST(TreeNode* root) {
    dfs(root);
    return res;
}

int main() {
    int rootVal;
    cin >> rootVal;
    unordered_map<int, TreeNode*> m;
    m[rootVal] = new TreeNode(rootVal);
    int nodeVal, leftVal, rightVal;
//     string str_line;
//     while (getline(cin, str_line)) {
//         stringstream ss(str_line);
//         string strNodeVal;
        
//         getline(ss, strNodeVal, ':');
//         int nodeVal = stoi(strNodeVal);
        
//         string strleftVal;
//         getline(ss, strleftVal, '|');
//         int leftVal = stoi(strleftVal);
        
//         string strrightVal;
//         getline(ss, strrightVal, '\n');
//         int rightVal = stoi(strrightVal);
        
//         if (!m.count(nodeVal)) {
//             m[nodeVal] = new TreeNode(nodeVal);
//         }
//         if (leftVal != -1) {
//             if (!m.count(leftVal)) m[leftVal] = new TreeNode(leftVal);
//             m[nodeVal]->left = m[leftVal];
//         }
//         if (rightVal != -1) {
//             if (!m.count(rightVal)) m[rightVal] = new TreeNode(rightVal);
//             m[nodeVal]->right = m[rightVal];
//         }
//     }
    
    while (scanf("%d:%d|%d", &nodeVal, &leftVal, &rightVal) != EOF) {
        if (!m.count(nodeVal)) {
            m[nodeVal] = new TreeNode(nodeVal);
        }
        if (leftVal != -1) {
            if (!m.count(leftVal)) m[leftVal] = new TreeNode(leftVal);
            m[nodeVal]->left = m[leftVal];
        }
        if (rightVal != -1) {
            if (!m.count(rightVal)) m[rightVal] = new TreeNode(rightVal);
            m[nodeVal]->right = m[rightVal];
        }
        if (cin.get() == '\n')
            if (cin.peek() == '\n') 
                break;
    }
    TreeNode *root = m[rootVal];
    cout << isBST(root) << endl;
    return 0;
}