CCI_chapter 4 trees and Grapths

4.1Implement a function to check if a tree is balanced For the purposes of this question,a balanced tree is defned to be a tree such that no two leaf nodes difer in distance from the root by more than one

 http://www.cnblogs.com/graph/archive/2013/04/12/3016433.html

4.2DFS

4.3Given a sorted (increasing order) array, write an algorithm to create a binary tree with  minimal height

http://www.cnblogs.com/graph/p/3184984.html

4.4 Given a binary search tree, design an algorithm which creates a linked list of all the nodes at each depth (eg, if you have a tree with depth D, you’ll have D linked lists)

http://www.cnblogs.com/graph/p/3251831.html

题目类似，就不多做了

4.5Write an algorithm to fnd the ‘next’ node (e g , in-order successor) of a given node in a binary search tree where each node has a link to its parent

struct Node
{
    int data;
    struct Node* left;
    struct Node* right;
    struct Node* parent;
};
Node * minNode(Node * cur){
    
    while(NULL != cur->left){
        cur = cur->left;
    }
    return cur;
    
}
Node * inOrderSucc(Node *cur){

    if(cur == NULL) return NULL;

    if(NULL != cur->right)
        return minNode(cur->right);
        
    Node * p = cur->parent;
    while(NULL != p && p->right == cur){
        cur = p;
        p = p->parent;
    }
    
    return p;

}

reference : http://www.geeksforgeeks.org/inorder-successor-in-binary-search-tree/(不喜欢CCI上的渣渣答案)

4.6Design an algorithm and write code to fnd the frst common ancestor of two nodes in a binary tree Avoid storing additional nodes in a data structure NOTE: This is not 

necessarily a binary search tree

http://www.cnblogs.com/graph/p/3271292.html

 

4.7 You have two very large binary trees: T1, with millions of nodes, and T2, with hundreds of nodes Create an algorithm to decide if T2 is a subtree of T1

无聊的一道题，解法完全没有体现出来大数据

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
bool isMatch(TreeNode * T1, TreeNode &T2); 
bool isSubtree(TreeNode *T1, TreeNode *T2){

    if(T2 == NULL) return true;
    if(NULL == T1) return false;
    if(T1->val == T2->val && ismatch(T1, T2)){
        return true;    
    }
    return isSubtree(T1->left , T2) || isSubtree(T1->right, T2) ;

}
bool isMatch(TreeNode * T1, TreeNode &T2){
    if(T1 == NULL && T2 == NULL) return true;
    if(T1 == NULL || T2 == NULL) return false;
    
    if(T1->val != T2->val) return false;
    
    return isMatch(T1->left , T2->right) && isMatch(T1->right, T2->right);

}

4.8 You are given a binary tree in which each node contains a value Design an algorithm  to print all paths which sum up to that value Note that it can be any path in the tree 

- it does not have to start at the root

CCI 给的答案实在不爽，明明就是一个后续遍历的应用。非要搞的莫名其妙的。

声明： 以下代码只是写出了我的思路，没有经过测试

struct Node{
    int val;
    Node * left;
    Node * right;
    Node(int value):val(value), left(NULL),right(NULL){}
};
void print(stack<int> s){
     while(!s.empty()){
            cout<<s.top() <<" ";
            s.pop();
    }
    cout<<endl;
}
void findSum(Node *root,int sum, vector<stack<int>> &path, vector<stack <int>> &path_sum ){

        if(root == NULL) return ;
        if(root->left == NULL && root->right == NULL){
            stack<int> p,s;
            p.push(root->val);
            s.push(root->val);
            path.push_back(p);
            path_sum.push_back(s);
            return;
        }
        
        vector<stack<int>> pathLeft, pathRight , sumLeft, sumRight;
        if(root->left != NULL)
                findSum(root->left, sum, pathLeft,sumLeft);
        if(root->right != NULL)
                findSum(root->right, sum, pathRight, sumRight);
        
        int cur = root->val;
        for(int i = 0; i < pathLeft.size(); i++)
        {
            pathLeft[i].push(cur);
            int top = sumLeft[i].top() + cur;
            sumLeft[i].push(top);
            if(top == sum)
                    print(pathLeft[i]);
                    
            path.push_back(pathLeft[i]);
            path_sum.push_back(sumLeft[i]);
        }
        
        for(int i = 0; i< pathRight.size(); i++)
        {
            pathRight[i].push_back(cur);
            int top = sumRight[i].top() + cur;
            sumRight[i].push(top);
            if(top == sum)
                print(pathRight[i]);
                
            path.push_back(pathRight[i]);
            path_sum.push_back(sumRight[i]);
        }
}