Number of reverse pairs in the statistical sequence C Language

<AlgorithmIntroduction> A Question in it. What I saw this morning.

For example, if a [0]> A [1], a [0] And a [1] are a reverse order. haha. as mentioned in the book, Merge Sorting is used. I implemented it.

The idea is clear and you are enjoying the process of studying algorithms.

/* 2-4-11-04-06-13.16.c -- Chapter 2, Topic 4 */<br/> # include <stdio. h> <br/> # include <stdlib. h> </P> <p> # define size (27) </P> <p> int main (void); <br/> int mergesort (int * const array, const int left, const int right); <br/> int Merge (int * const array, const int left, const int middle, const int right ); <br/> void printresult (const int * const array, const int size); </P> <p> int main (void) <br/> {<br/> int array [size] = {4, 2, 9, 7, 6, 3, 1, 5, 7, 54, 12, 87, 14, 62, 15, 0, 54, 33, 41, 87, 56, 43, 76, 53, 21, 46, 88}; <br/> int size = size; </P> <p> printf ("% d/N", mergesort (array, 0, size-1); <br/> printresult (array, size ); </P> <p> return 0; <br/>}</P> <p> int mergesort (int * const array, const int left, const int right) <br/>{< br/> static int COUNT = 0; <br/> int middle; </P> <p> If (left <right) <br/>{< br/> middle = (left + right)/2; <br/> mergesort (array, left, middle); <br/> mergesort (array, middle + 1, right); <br/> count + = Merge (array, left, middle, right); <br/> return count; <br/>}< br/> else <br/> return 0; <br/>}</P> <p> int Merge (int * const array, const int left, const int middle, const int right) <br/>{< br/> int * First, * Second; <br/> int flenth, slenth; <br/> int I, j, k; <br/> int count; </P> <p> flenth = middle-left + 1; <br/> slenth = right-middle; <br/> first = (int *) malloc (sizeof (INT) * flenth); <br/> second = (int *) malloc (sizeof (INT) * slenth); <br/> for (I = 0; I <flenth; I ++) <br/> first [I] = array [left + I]; <br/> for (j = 0; j <slenth; j ++) <br/> second [J] = array [Middle + J + 1]; <br/> COUNT = 0; <br/> I = J = 0; <br/> for (k = left; k <= right; k ++) <br/> {<br/> If (first [I] <= Second [J]) <br/> array [k] = first [I ++]; <br/> else <br/> {<br/> array [k] = Second [J ++]; <br/> count + = flenth-I; <br/>}< br/> if (I = flenth) <br/>{< br/> K ++; <br/> while (k <= right) <br/> array [k ++] = Second [J ++]; <br/> break; <br/>}< br/> else if (j = slenth) <br/>{< br/> K ++; <br/> while (k <= right) <br/> array [k ++] = first [I ++]; <br/> break; <br/>}< br/> free (first); <br/> free (second); </P> <p> return count; <br/>}</P> <p> void printresult (const int * const array, const int size) <br/>{< br/> int I; </P> <p> for (I = 0; I <size; I ++) <br/> printf ("%-3D", array [I]); <br/> putchar ('/N'); <br/>}