chore:flash-sort

Author: Orthodox-64

sorting/flash_sort.cpp

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+/**
+ * @file
+ * @brief Implementation of the Flash Sort algorithm.
+ * @details
+ * Flash Sort is an in-place, linear-time sorting algorithm for uniformly distributed data.
+ * It divides the data into classes, rearranges elements into their respective classes,
+ * and then sorts each class using insertion sort.
+ * @see https://en.wikipedia.org/wiki/Flashsort
+ * @note Flash Sort is not a stable sorting algorithm.
+ * @author [Sachin Pangal](https://github.com/orthodox-64)
+ */
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+/**
+ * @brief Sorts an array using the Flash Sort algorithm.
+ * @param arr The array to be sorted.
+ * @param n The number of elements in the array.
+ */
+ 
+ void flashSort(std::vector<float>& arr) {
+    int n = arr.size();
+    if (n <= 1) return;
+
+    // Step 1: Find the minimum and maximum values in the array
+    float minVal = *std::min_element(arr.begin(), arr.end());
+    float maxVal = *std::max_element(arr.begin(), arr.end());
+
+    // Step 2: Calculate the number of classes (buckets)
+    int numClasses = 0.45 * n;
+    if (numClasses < 2) numClasses = 2;
+
+    // Step 3: Create a histogram of the data
+    std::vector<int> count(numClasses, 0);
+    for (int i = 0; i < n; ++i) {
+        int index = numClasses * (arr[i] - minVal) / (maxVal - minVal);
+        count[index]++;
+    }
+
+    // Step 4: Calculate the starting index of each class
+    std::vector<int> pos(numClasses, 0);
+    pos[0] = 0;
+    for (int i = 1; i < numClasses; ++i) {
+        pos[i] = pos[i - 1] + count[i - 1];
+    }
+
+    // Step 5: Rearrange the array into classes
+    std::vector<float> temp = arr;
+    for (int i = 0; i < n; ++i) {
+        int index = numClasses * (arr[i] - minVal) / (maxVal - minVal);
+        arr[pos[index]++] = temp[i];
+    }
+
+    // Step 6: Sort each class using insertion sort
+    for (int i = 0; i < numClasses; ++i) {
+        int start = pos[i] - count[i];
+        int end = pos[i];
+        std::sort(arr.begin() + start, arr.begin() + end);
+    }
+}
+
+// Driver code to test the Flash Sort
+int main() {
+    std::vector<float> arr = {0.897, 0.565, 0.656, 0.1234, 0.665, 0.3434};
+    flashSort(arr);
+
+    std::cout << "Sorted array is: ";
+    for (float num : arr) {
+        std::cout << num << " ";
+    }
+    return 0;
+}