The Divide and conquer approach-merge sort

1 The divide  and conquer approach-  Merge sort
2 The theory of merging sort is called divide-and-conquer method.3 The idea of divide-and-conquer method is to decompose the problem into several sub-problems, which are smaller in size and similar to the original one .4 then recursion (recursive) solves these sub-problems, and finally merges the solutions of these sub-problems to obtain5 solution to the original problem.6That is, decomposition--merge.7 8The Divide andConquer approach9Decomposition: The sequence of n elements to be sorted is decomposed into two n/2 with atwo sub-sequences.Ten Workaround: Sort two sub-sequences recursively by using merge sort. One Merge: Merges two sorted sub-sequences to derive results. A  -The merge sort algorithm'Complexity of Time'It's Nlogn . -  the ImportTime , Random -  - defSortdivide (alist):#decomposition divide -     ifLen (alist) <= 1: +         returnalist -L1 = Sortdivide (alist[:alist.__len__()//2]) +L2 = Sortdivide (alist[alist.__len__()//2:]) A     returnSortmerge (L1,L2) at  - defSortmerge (L1, L2):#Resolve & Merge Sort & Merge -ListS = [] -     Print("Left -", L1) -     Print("Right -", L2) -I,j =0,0 in      whileI < L1.__len__() andJ < L2.__len__(): -         ifL1[i] <=L2[j]: to lists.append (L1[i]) +i + = 1 -             Print("- I.", i) the         Else: * lists.append (L2[j]) $J + = 1Panax Notoginseng             Print("-j", J) -         Print(ListS) the     Else: +         ifi = = L1.__len__(): A lists.extend (l2[j:]) the         Else: + lists.extend (l1[i:]) -         Print(ListS) $     Print("Product-", ListS) $     returnListS -  - defrandomlist (n,r): theF =0 -Rlist = []Wuyi      whileF <N: theF + = 1 - rlist.append (Random.randrange (0,r)) Wu     returnrlist -  About if __name__=="__main__": $Alist = Randomlist (9,100) -     Print("List-o", Alist) -Startt =time.time () -     Print("list-s", Sortdivide (alist)) AEndt =time.time () +     Print("Time Elapsed:", Endt-Startt) the  - output, $List-o [88, 79, 52, 78, 0, 43, 21, 55, 62] theLeft-[88] theRight-[79] the-j 1 the[79] -[79, 88] inProduct-[79, 88] theLeft-[52] theRight-[78] About-I. 1 the[52] the[52, 78] theProduct-[52, 78] +Left-[79, 88] -Right-[52, 78] the-j 1Bayi[52] the-j 2 the[52, 78] -[52, 78, 79, 88] -Product-[52, 78, 79, 88] theLeft-[0] theRight-[43] the-I. 1 the [0] -[0, 43] theProduct-[0, 43] theLeft-[55] theRight-[62]94-I. 1 the[55] the[55, 62] theProduct-[55, 62]98Left-[21] AboutRight-[55, 62] --I. 1101[21]102[21, 55, 62]103Product-[21, 55, 62]104Left-[0, 43] theRight-[21, 55, 62]106-I. 1107 [0]108-j 1109[0, 21] the-I. 2111[0, 21, 43] the[0, 21, 43, 55, 62]113Product-[0, 21, 43, 55, 62] theLeft-[52, 78, 79, 88] theRight-[0, 21, 43, 55, 62] the-j 1117 [0]118-j 2119[0, 21] --j 3121[0, 21, 43]122-I. 1123[0, 21, 43, 52]124-j 4 the[0, 21, 43, 52, 55]126-j 5127[0, 21, 43, 52, 55, 62] -[0, 21, 43, 52, 55, 62, 78, 79, 88]129Product-[0, 21, 43, 52, 55, 62, 78, 79, 88] thelist-s [0, 21, 43, 52, 55, 62, 78, 79, 88]131Time elapsed:0.0010027885437011719

The Divide and conquer approach-merge sort