24.cpp

data_structure/24.cpp

@@ -0,0 +1,75 @@
+/*
+二叉排序树的判别
+*/
+#include<iostream>
+using namespace std;
+struct TreeNode{
+    int val;
+    struct TreeNode *left, *right;
+};
+class tree{
+    public:
+        struct TreeNode *root;
+        void pre_create(struct TreeNode* &tr);
+        tree();
+        bool judge(struct TreeNode *tr);
+        void pre(struct TreeNode *tr);
+};
+tree::tree(){
+    root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
+}
+void tree::pre_create(struct TreeNode* &tr){         //根据先序序列创建树
+    int c;
+    cin>>c;
+    if(c != EOF){
+        if(c == -1){
+            tr = NULL;
+            //tr->left = tr->right = NULL;
+            return;
+        }
+        tr = (struct TreeNode*)malloc(sizeof(struct TreeNode));
+        tr->val = c;
+        tr->left = tr->right = NULL;
+        // tr->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
+        // tr->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
+        pre_create(tr->left);
+        pre_create(tr->right);
+    }
+}
+//判断是否是二叉排序树
+bool tree::judge(struct TreeNode *tr){
+    if(tr == NULL)  return true;
+
+    struct TreeNode *tmp = tr->left;
+    //左子树最大的结点
+    while(tmp != NULL && tmp->right != NULL){
+        tmp = tmp->right;
+    }
+    if(tmp != NULL && tmp->val > tr->val)    return false;
+
+    //右子树最小的结点
+    tmp = tr->right;
+    while(tmp != NULL && tmp->left != NULL){
+        tmp = tmp->left;
+    }
+    if(tmp != NULL && tmp->val < tr->val)    return false;
+
+    return judge(tr->left)&&judge(tr->right);
+}
+
+void tree::pre(struct TreeNode *tr){
+    if(tr){
+        cout<<tr->val<<" ";
+        pre(tr->left);
+        pre(tr->right);
+    }
+}
+int main()
+{
+    tree T;
+    T.pre_create(T.root);
+    T.judge(T.root)? cout<<"yes"<<endl : cout<<"no"<<endl;
+    //T.pre(T.root);
+    return 0;
+}
+