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April 16, 2019 14:41
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C++ Merge Sort implementation
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/* C program for Merge Sort */ | |
#include<stdlib.h> | |
#include<stdio.h> | |
// Merges two subarrays of arr[]. | |
// First subarray is arr[l..m] | |
// Second subarray is arr[m+1..r] | |
void merge(int arr[], int l, int m, int r) | |
{ | |
int i, j, k; | |
int n1 = m - l + 1; | |
int n2 = r - m; | |
/* create temp arrays */ | |
int L[n1], R[n2]; | |
/* Copy data to temp arrays L[] and R[] */ | |
for (i = 0; i < n1; i++) | |
L[i] = arr[l + i]; | |
for (j = 0; j < n2; j++) | |
R[j] = arr[m + 1+ j]; | |
/* Merge the temp arrays back into arr[l..r]*/ | |
i = 0; // Initial index of first subarray | |
j = 0; // Initial index of second subarray | |
k = l; // Initial index of merged subarray | |
while (i < n1 && j < n2) | |
{ | |
if (L[i] <= R[j]) | |
{ | |
arr[k] = L[i]; | |
i++; | |
} | |
else | |
{ | |
arr[k] = R[j]; | |
j++; | |
} | |
k++; | |
} | |
/* Copy the remaining elements of L[], if there | |
are any */ | |
while (i < n1) | |
{ | |
arr[k] = L[i]; | |
i++; | |
k++; | |
} | |
/* Copy the remaining elements of R[], if there | |
are any */ | |
while (j < n2) | |
{ | |
arr[k] = R[j]; | |
j++; | |
k++; | |
} | |
} | |
/* l is for left index and r is right index of the | |
sub-array of arr to be sorted */ | |
void mergeSort(int arr[], int l, int r) | |
{ | |
if (l < r) | |
{ | |
// Same as (l+r)/2, but avoids overflow for | |
// large l and h | |
int m = l+(r-l)/2; | |
// Sort first and second halves | |
mergeSort(arr, l, m); | |
mergeSort(arr, m+1, r); | |
merge(arr, l, m, r); | |
} | |
} | |
/* UTILITY FUNCTIONS */ | |
/* Function to print an array */ | |
void printArray(int A[], int size) | |
{ | |
int i; | |
for (i=0; i < size; i++) | |
printf("%d ", A[i]); | |
printf("\n"); | |
} | |
/* Driver program to test above functions */ | |
int main() | |
{ | |
int arr[] = {12, 11, 13, 5, 6, 7}; | |
int arr_size = sizeof(arr)/sizeof(arr[0]); | |
printf("Given array is \n"); | |
printArray(arr, arr_size); | |
mergeSort(arr, 0, arr_size - 1); | |
printf("\nSorted array is \n"); | |
printArray(arr, arr_size); | |
return 0; | |
} |
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