diff --git a/sorting/binary_insertion_sort.cpp b/sorting/binary_insertion_sort.cpp new file mode 100644 index 000000000..23ab216a2 --- /dev/null +++ b/sorting/binary_insertion_sort.cpp @@ -0,0 +1,139 @@ +/** + * \file + * \brief [Binary Insertion Sort Algorithm + * (Insertion Sort)](https://en.wikipedia.org/wiki/Insertion_sort) + * + * \details + * If the cost of comparisons exceeds the cost of swaps, as is the case for example with * string keys stored by reference or with human interaction (such as choosing one of a pair * displayed side-by-side), then using binary insertion sort may yield better performance. * Binary insertion sort employs a binary search to determine the correct location to insert * new elements, and therefore performs ⌈log2 n⌉ comparisons in the worst case. When each * element in the array is searched for and inserted this is O(n log n). + * The algorithm as a whole still has a running time of O(n2) on average because of the series * of swaps required for each insertion. + * However it has several advantages such as + * 1. Easy to implement + * 2. For small set of data it is quite efficient + * 3. More efficient that other Quadratic complexity algorithms like + * Selection sort or bubble sort. + * 4. It is efficient to use it when the cost of comparison is high. + * 5. It's stable that is it does not change the relative order of + * elements with equal keys. + * 6. It can sort the array or list as it receives. + * + * Example execution steps: + * 1. Suppose initially we have + * \f{bmatrix}{40 &30 &20 &50 &10\f} + * 2. We start traversing from 40 till we reach 10 + * when we reach at 30 we find that it is not at it's correct place so we take 30 and place + * it at a correct position thus the array will become + * \f{bmatrix}{30 &40 &20 &50 &10\f} + * 3. In the next iteration we are at 20 we find that this is also misplaced so + * we place it at the correct sorted position thus the array in this iteration + * becomes + * \f{bmatrix}{20 &30 &40 &50 &10\f} + * 4. We do not do anything with 50 and move on to the next iteration and + * select 10 which is misplaced and place it at correct position. Thus, we have + * \f{bmatrix}{10 &20 &30 &40 &50\f} + */ + +#include +#include +#include +#include + +/** + * \namespace sorting + * @brief Sorting algorithms + */ +namespace sorting { + +/** + * \brief Binary search function to find the most suitable pace for an element. + * \tparam T The generic data type. + * \param arr The actual vector in which we are searching a suitable place for the element. + * \param val The value for which suitable place is to be found. + * \param low The lower bound of the range we are searching in. + * \param high The upper bound of the range we are searching in. + * \returns the index of most suitable position of val. + */ +template +int binary_search(std::vector &arr,T val,int low,int high) +{ + if (high <= low) + return (val > arr[low]) ? (low + 1) : low; + + int mid = low + (high-low)/2; + if(arr[mid]>val) + return binary_search(arr,val,low,mid-1); + else if(arr[mid] +void insertionSort_binsrch(std::vector &arr) { + int n = arr.size(); + + for (int i = 1; i < n; i++) { + T key = arr[i]; + int j = i - 1; + int loc = sorting::binary_search(arr,key,0,j); + while (j >= loc) { + arr[j + 1] = arr[j]; + j--; + } + arr[j + 1] = key; + } +} +} // namespace sorting + +/** + * @brief Self-test implementations + * @returns void + */ +void test() { + /* descriptions of the following test */ + /* 1st test: + [5, -3, -1, -2, 7] returns [-3, -2, -1, 5, 7] */ + std::vector arr1({5, -3, -1, -2, 7}); + std::cout << "Test 1... "; + sorting::insertionSort_binsrch(arr1); + assert(std::is_sorted(std::begin(arr1), std::end(arr1))); + std::cout << "passed" << std::endl; + + /* 2nd test: + [12, 26, 15, 91, 32, 54, 41] returns [12, 15, 26, 32, 41, 54, 91] */ + std::vector arr2({12, 26, 15, 91, 32, 54, 41}); + std::cout << "Test 2... "; + sorting::insertionSort_binsrch(arr2); + assert(std::is_sorted(std::begin(arr2), std::end(arr2))); + std::cout << "passed" << std::endl; + + /* 3rd test: + [7.1, -2.5, -4.0, -2.1, 5.7] returns [-4.0, -2.5, -2.1, 5.7, 7.1] */ + std::vector arr3({7.1, -2.5, -4.0, -2.1, 5.7}); + std::cout << "Test 3... "; + sorting::insertionSort_binsrch(arr3); + assert(std::is_sorted(std::begin(arr3), std::end(arr3))); + std::cout << "passed" << std::endl; + + /* 4th test: + [12.8, -3.7, -20.7, -7.1, 2.2] returns [-20.7, -7.1, -3.7, 2.2, 12.8] */ + std::vector arr4({12.8, -3.7, -20.7, -7.1, 2.2}); + std::cout << "Test 4... "; + sorting::insertionSort_binsrch(arr4); + assert(std::is_sorted(std::begin(arr4), std::end(arr4))); + std::cout << "passed" << std::endl; +} + +/** + * @brief Main function + * @return 0 on exit. + */ +int main() { + test(); // run self-test implementations + return 0; +}