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Update count_inversions.cpp

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This commit is contained in:
Rakshit Raj
2020-12-04 03:33:21 +05:30
committed by GitHub
parent ecd5c9fb44
commit 121ce330ef
1 changed files with 27 additions and 23 deletions
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50
sorting/count_inversions.cpp
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@@ -63,8 +63,11 @@ namespace inversion {
// void show(int* arr, const int size);
/**
* Function to merge two sub-arrays. merge() function is called
* from mergeSort() to merge the array after it split for sorting
* @brief Function to merge two sub-arrays.
*
* @details
* merge() function is called from mergeSort()
* to merge the array after it split for sorting
* by the mergeSort() funtion.
*
* In this case the merge fuction will also count and return
@@ -79,7 +82,7 @@ namespace inversion {
* @returns number of inversions found in merge step
*/
template <typename T>
uint64_t merge(T* arr, T* temp, uint32_t left, uint32_t mid, uint32_t right) {
uint32_t merge(T* arr, T* temp, uint32_t left, uint32_t mid, uint32_t right) {
uint32_t i = left; /* i --> index of left sub-array */
uint32_t j = mid + 1; /* j --> index for right sub-array */
uint32_t k = left; /* k --> index for resultant array temp */
@@ -110,7 +113,9 @@ uint64_t merge(T* arr, T* temp, uint32_t left, uint32_t mid, uint32_t right) {
}
/**
*
* @brief Implement merge Sort and count inverions while merging
*
* @details
* The mergeSort() function implements Merge Sort, a
* Divide and conquer algorithm, it divides the input
* array into two halves and calls itself for each
@@ -124,7 +129,7 @@ uint64_t merge(T* arr, T* temp, uint32_t left, uint32_t mid, uint32_t right) {
* @returns number of inversions in array
*/
template <typename T>
uint64_t mergeSort(T* arr, T* temp, uint32_t left, uint32_t right) {
uint32_t mergeSort(T* arr, T* temp, uint32_t left, uint32_t right) {
uint32_t mid = 0, inv_count = 0;
if (right > left) {
// midpoint to split the array
@@ -145,7 +150,6 @@ uint64_t mergeSort(T* arr, T* temp, uint32_t left, uint32_t right) {
* how close or far off the array is to being sorted.
*
* @details
* @details
* Number of inversions in a sorted array is 0.
* Number of inversion in an array[1...n] sorted in
* non-ascending order is n(n-1)/2, since each pair of elements
@@ -157,7 +161,7 @@ uint64_t mergeSort(T* arr, T* temp, uint32_t left, uint32_t right) {
* @returns number of inversions in input array, sorts the array
*/
template <class T>
uint32_t countInversion(T* arr, const uint16_t size) {
uint32_t countInversion(T* arr, const uint32_t size) {
std::vector<T> temp;
temp.reserve(size);
temp.assign(size, 0);
@@ -174,7 +178,7 @@ uint32_t countInversion(T* arr, const uint16_t size) {
template <typename T>
void show(T* arr, const uint32_t array_size) {
std::cout << "Printing array: \n";
for (uint64_t i = 0; i < array_size; i++) {
for (uint32_t i = 0; i < array_size; i++) {
std::cout << " " << arr[i];
}
std::cout << "\n";
@@ -196,28 +200,28 @@ static void test() {
49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33,
32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16,
15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
uint16_t size1 = arr1.size();
uint32_t size1 = arr1.size();
uint32_t inv_count1 = 4950;
uint64_t result1 = sorting::inversion::countInversion(arr1.data(), size1);
uint32_t result1 = sorting::inversion::countInversion(arr1.data(), size1);
assert(inv_count1 == result1);
// Test 2
std::vector<int> arr2 = {22, 66, 75, 23, 11, 87, 2, 44, 98, 43};
uint16_t size2 = arr2.size();
uint32_t size2 = arr2.size();
uint32_t inv_count2 = 20;
uint64_t result2 = sorting::inversion::countInversion(arr2.data(), size2);
uint32_t result2 = sorting::inversion::countInversion(arr2.data(), size2);
assert(inv_count2 == result2);
// Test 3
std::vector<double> arr3 = {33.1, 45.2, 65.4, 76.5, 1.0,
2.9, 5.4, 7.7, 88.9, 12.4};
uint16_t size3 = arr3.size();
uint32_t size3 = arr3.size();
uint32_t inv_count3 = 21;
uint64_t result3 = sorting::inversion::countInversion(arr3.data(), size3);
uint32_t result3 = sorting::inversion::countInversion(arr3.data(), size3);
assert(inv_count3 == result3);
// Test 4
std::vector<char> arr4 = {'a', 'b', 'c', 'd', 'e'};
uint16_t size4 = arr4.size();
uint32_t size4 = arr4.size();
uint32_t inv_count4 = 0;
uint64_t result4 = sorting::inversion::countInversion(arr4.data(), size4);
uint32_t result4 = sorting::inversion::countInversion(arr4.data(), size4);
assert(inv_count4 == result4);
}
@@ -228,33 +232,33 @@ static void test() {
// template <typename T>
// static void body() {
// // Input your own sequence
// uint64_t size;
// uint_t size;
// T input;
// std::cout << "Enter number of elements:";
// std::cin >> size;
//
// std::vector<T> arr;
// arr.reserve(size);
//
// std::cout << "Enter elements -->\n";
// for (uint64_t i=1; i<=size; i++) {
// std::cout << "Element "<< i <<" :";
// std::cin >> input;
// arr.push_back(input);
// }
//
// if (size != arr.size()) {
// size = arr.size();
// }
//
// std::cout << "\n";
// sorting::inversion::show(arr.data(), size);
// std::cout << "\n";
//
// // Counting inversions
// std::cout << "\nThe number of inversions: "<<
// sorting::inversion::countInversion(arr.data(), size) << "\n";
//
// // Output sorted array
// std::cout << "\nSorted array --> \n";
// sorting::inversion::show(arr.data(), size);