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18. 4Sum I (32lines) Given a integer array and target, find all unique quadruplets sum is target. Solution(O(N^3)): Similar as 3sum problem, add one m 阅读全文
摘要：
1. Think carefully about the variables used for different range, they may represent same value in the meaning, but they are used in different range, s 阅读全文
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3Sum Given a integer array, find all the unique 3-number pairs which sum = 0. Solution O(N^2): 1. Sort the array, and makes this problem to a equal '2 阅读全文