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Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the 阅读全文
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Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the hist 阅读全文
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Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Note: Do not modify the linked list. 阅读全文
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Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 阅读全文
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Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another e 阅读全文
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Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the lo 阅读全文