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https://leetcode.com/problems/remove-element/#/description Given an array and a value, remove all instances of that value in place and return the new 阅读全文
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https://leetcode.com/problemset/all/?search=19 涉及链表删除操作的时候，稳妥起见都用 dummynode，省去很多麻烦。因为不一定什么时候 head 就被删了。 快慢指针 阅读全文
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https://leetcode.com/problems/4sum/#/solutions Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target 阅读全文
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Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. 阅读全文
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为何不像76. Minimum Window Substring用数组来匹配, 是因为双指针是根据字符串的顺序遍历的, 而数组的话没有顺序.如 For example,S = "ADOBECODEBANC"T = "ABC" Minimum window is "BANC". 并不是非得ABC的顺序 阅读全文