LeetCode :: Convert Sorted Array (link list) to Binary Search Tree [tree]

标签：leetcode   c++   递归   tree   

1.Array

class Solution {
public:
    TreeNode *Tree(int left, int right, vector<int> &num){
        TreeNode *root = NULL;
        if (left <= right){
            int cen = (left + right) / 2;
            root = new TreeNode(num[cen]);
            root->left = Tree(left, cen - 1, num);
            root->right = Tree(cen + 1, right, num);
        }
        return root;
    }
    
    TreeNode *sortedArrayToBST(vector<int> &num) {
        TreeNode *T = NULL;
        int N = num.size();
        T = Tree(0, N - 1, num);
        return T;
    }
};

class Solution {
public:
    ListNode *findMid(ListNode *head){        //这里如果链表中只有两个数字，则mid返回的是head->next.
        if (head == NULL || head -> next == NULL)
            return head;
        ListNode *fast, *slow, *pre;
        fast = slow = head;
        pre = NULL;
        while (fast && fast->next){
            pre = slow;
            slow = slow->next;
            fast = fast->next->next;
        }
        pre->next = NULL;
        return slow;
    }
    
    TreeNode *buildTree(ListNode *head){
        TreeNode *root = NULL;
        ListNode *mid = NULL;
        if (head){
            mid = findMid(head);
            root = new TreeNode(mid->val);
            if (head != mid){
                root->left = buildTree(head);
                root->right = buildTree(mid->next);
            }
        }
        return root;
        
    }
    
    TreeNode *sortedListToBST(ListNode *head) {
        TreeNode *T;
        T = buildTree(head);
        return T;
    }
};

LeetCode :: Convert Sorted Array (link list) to Binary Search Tree [tree]

标签：leetcode   c++   递归   tree   

原文地址：http://blog.csdn.net/u013195320/article/details/38025543