Merge sort and statistic array reverse order



1. Merge Sort

Introduction to the algorithm (P19 )

Reference URL:

The realization of the five merging sort of the classical algorithm series of vernacular -morewindows blog- blog channel -csdn.net

http://blog.csdn.net/morewindows/article/details/6678165

#include "stdafx.h" #include <iostream>using std::cout; #define Array_length 11//sort two ordered arrays//Parameters: Data original array, Copy combined into an array, Start,mid,end records the position of two arrays in the original array//mid represents the cutoff position of the first array void Merge (int data[],int copy[],size_t start,size_t mid,si  ze_t end) {//Determine if the input parameters are valid if (data! = nullptr) && (copy! = nullptr) && (Start <= mid) && (Mid <    End) {size_t i = start;  Left array start position size_t j = mid + 1; Right array start position size_t index = start;//Auxiliary array start position while ((I <= mid) && (J <= End) {//Compare two values, the smaller ones into the auxiliary array, and move the pointer forward if (data[ I] <= data[j]) {copy[index++] = data[i++];} else{copy[index++] = data[j++];}} Handles one array traversal, and another array with remaining elements while (I <= mid) {copy[index++] = data[i++];} while (J<=end) {copy[index++] = data[j++];} Collate the sorted data array for (size_t k = 0; k <= end; k++) {data[k] = copy[k];}} Merge algorithm core algorithm void Merge_sort (int data[], int copy[], size_t start, size_t end) {if (data! nullptr) && (copy! = NULL PTR) {if (Start < end) {size_t mid = (start + end)/2;//thought Merge_sort (Data, copy, start, mid); Merge_sort (data, copy, Mid + 1, end);//array sort merge (data, copy, start, Mid, End);}} Else{cout << "Array parameter input error";}} Print array void Printf_array (int data[], size_t length) {for (size_t i = 0; i < length; i++) {cout << data[i] << s Td::endl;}} int _tmain (int argc, _tchar* argv[]) {int data[] = {10,32,9,1,23,42,5,67,88,23,7};//printf_array (data, array_length); int copy[array_length]; Merge_sort (data, copy, 0, array_length-1);p rintf_array (data, array_length); return 0;}

2. using merge sorting to handle related problems, the inverse of the statistics array

"Sword Point offer"P191

InversePais1.cpp: Computes the inverse of an array of n elements to//#include "stdafx.h"//calculates the inverse of the function int get_inversepairs (int data[],int copy[],size_t start,size_t mid,size_t end) {int count = 0;//to determine if the array is empty, and whether the input position parameter is valid if (data!=nullptr) && (copy!=nullptr) &  & (Start <= mid) && (Mid < end)) {int i = mid;int J = End;int index = end;while ((i >= start) && (j >= mid + 1) && (i * J >= 0)) {//Compare whichever is most, put in the secondary array of the lowest if (Data[i] > Data[j]) {copy[index--] = Data[i--];count + = ( J-MID);//reverse to statistics}else{copy[index--] = data[j--];//This time indicates that the latter is greater than the former, does not meet the definition of reverse order, so count does not operate}}//processing the remaining array (note: This situation count will no longer change, As already counted fully) while ((I >= start) && (i >= 0)) {copy[index--] = data[i--];} while ((J >= mid + 1) && (J >= 0)) {copy[index--] = data[j--];} printf ("Raw data:"); for (size_t k = start; K <= End; k++) {printf ("%d", Data[k]);} printf ("\ n Current data:"); for (size_t k = start; K <= End; k++) {Data[k] = Copy[k];p rintf ("%d", Data[k]);} printf ("\ n");p rintf ("Inverse logarithm:%d\n", count);} return count;} int Reverse_pairs (int data[], int copy[], size_t start, size_t end) {if (data = = nullptr) | | (copy = = nullptr)) {return 0;} if (start >= end) {return 0;} Divide-and-conquer strategy int mid = (start + end)/2;int left = reverse_pairs (data, copy, start, mid); int right = Reverse_pairs (data, copy, M ID + 1, end); int count = get_inversepairs (data, copy, start, Mid, end); return left + right + count;} int _tmain (int argc, _tchar* argv[]) {int data[] = {7,5,6,4};const size_t LENGTH = 4;int Copy[length];p rintf ("%d\n", revers E_pairs (data, copy, 0, LENGTH-1)); return 0;}

Merge sort and statistic array reverse order