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Given a binary search tree, return a balanced binary search tree with the same node values. A binary search tree is balanced if and only if the depth 阅读全文
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Given a non-negative integer, you could swap two digits at most once to get the maximum valued number. Return the maximum valued number you could get. 阅读全文
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Given a string S of '(' and ')' parentheses, we add the minimum number of parentheses ( '(' or ')', and in any positions ) so that the resulting paren 阅读全文
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Given a robot cleaner in a room modeled as a grid. Each cell in the grid can be empty or blocked. The robot cleaner with 4 given APIs can move forward 阅读全文
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Given an integer array nums which is sorted in ascending order and all of its elements are unique and given also an integer k, return the kth missing 阅读全文
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You need to construct a binary tree from a string consisting of parenthesis and integers. The whole input represents a binary tree. It contains an int 阅读全文
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Given the root of a binary tree, determine if it is a complete binary tree. In a complete binary tree, every level, except possibly the last, is compl 阅读全文