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动态规划属于技巧性比较强的题目，如果看到过原题的话，对解题很有帮助 55. Jump Game Given an array of non-negative integers, you are initially positioned at the first index of the array. 阅读全文
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一般用dfs来做 最简单的一种： 17. Letter Combinations of a Phone Number Given a digit string, return all possible letter combinations that the number could represe 阅读全文
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需要注意overflow，特别是Integer.MIN_VALUE这个数字。 需要掌握二分法。 不用除法的除法，分而治之的乘方 2. Add Two Numbers You are given two linked lists representing two non-negative number 阅读全文
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Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following unique pe 阅读全文