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摘要： How it worksDivide: Partition the array into two subarrays around a pivot x such that elements in lower subarray ≤ x ≤ elements in upper subarray.Conquer: Recursively sort the two subarrays.Combine: Trivial.How to divide(Assume the array is start at p and end at q)1. First gives two pointer i j , i 阅读全文

摘要： Steps:Divide the problem (instance) into subproblems.Conquer the subproblems by solving them recursively.Combine subproblem solutions.A typical algorithm solved by D&V is merge sort. Frist we partitions the array into two sorted array recursivly, that is the Dvide part.Then we combine the two so 阅读全文

摘要： There are 3 methods to work out a Recurrence.Substitution method.Steps:Guess the result.Prove it by induction.Ex: T(n) = 4T(n/2) + n[Assume that T(1) = Θ(1)]Guess O(n3) . (Prove O and Ω separately.)Assume that T(k) ≤ ck3 for k < n .Prove T(n) ≤ cn3 by induction.T (n) = 4T (n / 2) + n ≤ 4c ( n / 2 阅读全文