leetcode Ch4-Binary Tree & BFS & Divide/Conquer

一、

1. Lowest Common Ancestor

class BSTIterator {
public:
BSTIterator(TreeNode* root) {
pushAll(root);
}

bool hasNext() {
return (!myStack.empty());
}

int next() {
TreeNode* tmp = myStack.top();
myStack.pop();
pushAll(tmp->right);
return tmp->val;
}

private:
stack<TreeNode*> myStack;
void pushAll(TreeNode* node);
};

void BSTIterator::pushAll(TreeNode* node) {
while (node != NULL) {
myStack.push(node);
node = node->left;
}
}

/**
* Your BSTIterator will be called like this:
* BSTIterator i = BSTIterator(root);
* while (i.hasNext()) cout << i.next();
*/

View Code

Remove Node in Binary Search Tree

Binary Tree Maximum Path Sum

参见 ref 十五

Binary Tree Serialization

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对于n个数的数组，一个数x如果从左往右数是第k个数，那么从右往左数的话是第(n - k + 1)个数。