Add example for radix sort

cpp/algorithms/sorting/CMakeLists.txt

@@ -23,3 +23,4 @@ add_subdirectory(heap)
 add_subdirectory(quick)
 add_subdirectory(count)
 add_subdirectory(bucket)
+add_subdirectory(radix)

cpp/algorithms/sorting/radix/CMakeLists.txt

@@ -0,0 +1,19 @@
+###############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: A basic CMakeLists configuration to practice radix sort            ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+###############################################################################
+
+cmake_minimum_required(VERSION 3.16)
+project(RadixSort LANGUAGES CXX)
+
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+
+add_executable(radix-sort "radix-sort.cpp")
+
+add_library(lib-counting "lib-counting.cpp")
+add_library(lib-radix "lib-radix.cpp")
+
+target_link_libraries(radix-sort lib-radix lib-counting)

cpp/algorithms/sorting/radix/lib-counting.cpp

@@ -0,0 +1,65 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: An example implementation of counting sort using a custom library  ##
+##        + In support of a radix sort implementation                        ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+###############################################################################
+*/
+
+#include "lib-counting.hpp"
+
+#include <algorithm>
+#include <vector>
+#include <cstdint>
+
+
+void CountingSort(std::vector<int> &array, int placeValue)
+{
+  std::vector<int> sortedArray(array.size(), 0);
+
+  // Find the maximum value within the array to sort
+  int32_t maxValue = INT32_MIN;
+  for (const auto &val : array) maxValue = (val > maxValue) ? val : maxValue;
+
+  // Create an array with element for all *placeValues* within range of the set
+  // + Not the size of the array to sort, but instead a element of
+  // + tempArray[digit] = 0; Considering only the digit at placeValue of array[n]
+  // Using this vector, we have a place to count all possible digits at placeValue
+  std::vector<int> tempArray(10, 0);
+
+  // Count the occurrences of each digit at this placeValue within the array
+  // + Store the end result as tempArray[digit] = count;
+  // + Where digit is found at the decimal placeValue of each value within array
+  for (const auto &val : array) {
+    // Get the digit at the decimal placeValue of arrayValue
+    auto index = static_cast<size_t>((val / placeValue) % tempArray.size());
+    // Running total of each value with the same digit at decimal placeValue
+    tempArray[index] = tempArray[index] + 1;
+  }
+
+  // Count the values less than or equal to each element of tempArray
+  // + Since each element stores its own count, just add the count at index i-1
+  for (int i = 1; i < tempArray.size(); i++) {
+    tempArray[i] = tempArray[i] + tempArray[i - 1];
+  }
+
+  for (ssize_t arrayIndex = array.size() - 1; arrayIndex >= 0; arrayIndex--) {
+    // Get the value to consider from the unsorted array
+    const int &arrayValue = array[arrayIndex];
+
+    // Get the digit at the decimal placeValue of arrayValue
+    // + Use this index to update count of values as we use them
+    const auto tempIndex =
+        static_cast<size_t>((arrayValue / placeValue) % tempArray.size());
+
+    // Store valueCount as a reference so we can update it
+    int &valueCount = tempArray[tempIndex];
+    // Offset valueCount by 1 to allow for zero index of sortedArray
+    sortedArray[valueCount - 1] = arrayValue;
+    valueCount = valueCount - 1;
+  }
+
+  array = sortedArray;
+}

cpp/algorithms/sorting/radix/lib-counting.hpp

@@ -0,0 +1,19 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: An example implementation of counting sort using a custom library  ##
+##        + In support of a radix sort implementation                        ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+###############################################################################
+*/
+
+#ifndef RADIX_LIB_COUNT_HPP
+#define RADIX_LIB_COUNT_HPP
+
+#include <vector>
+
+
+void CountingSort(std::vector<int> &array, int placeValue);
+
+#endif // RADIX_LIB_COUNT_HPP

cpp/algorithms/sorting/radix/lib-radix.cpp

@@ -0,0 +1,29 @@
+
+#include "lib-radix.hpp"
+#include "lib-counting.hpp"
+
+#include <algorithm>
+#include <vector>
+
+
+void RadixSort(std::vector<int> &array)
+{
+  int maxValue = *std::max_element(array.begin(), array.end());
+  // Get the total number of digits in the maximum value within the set
+  // + 100 has 3 digits; 10 has 2 digits; etc..
+  int digits = 0;
+  for (int tempMax = maxValue; tempMax > 0; tempMax /= 10) digits++;
+
+  // For each placeValue of the maximum value within the set
+  for (int placeValue = 1; maxValue / placeValue > 0; placeValue *= 10) {
+    // Perform counting sort on all values, only considering the placeValue digit
+    // Result of sorting the first placeValue:
+    // + 12, 10, 15, 5, 3, 101, 109, 115 -> 10, 101, 12, 3, 115, 15, 5, 109
+    // Result of sorting the second placeValue:
+    // + 10, 101, 12, 3, 115, 15, 5, 109 -> 3, 5, 101, 109, 10, 12, 115, 15
+    // Result of sorting the third placeValue:
+    // + 3, 5, 101, 109, 10, 12, 115, 15 -> 3, 5, 10, 12, 15, 101, 109, 115
+    CountingSort(array, placeValue);
+  }
+
+}

cpp/algorithms/sorting/radix/lib-radix.hpp

@@ -0,0 +1,18 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: An example implementation of radix sort using a custom library     ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+###############################################################################
+*/
+
+#ifndef LIB_RADIX_HPP
+#define LIB_RADIX_HPP
+
+#include <vector>
+
+
+void RadixSort(std::vector<int> &array);
+
+#endif // LIB_RADIX_HPP

cpp/algorithms/sorting/radix/radix-sort.cpp

@@ -0,0 +1,45 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: An example implementation of radix sort using a custom library     ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+###############################################################################
+*/
+
+#include "lib-counting.hpp"
+#include "lib-radix.hpp"
+
+#include <algorithm>
+#include <vector>
+#include <random>
+#include <iostream>
+
+// More values increase chance that the set provides colliding placeValue digits
+#define ARRAY_LENGTH 20
+
+
+int main(const int argc, const char * argv[])
+{
+  srand(time(nullptr));
+  std::vector<int> array(ARRAY_LENGTH);
+  // For this example, we limit the maximum value to 150
+  // + This helps to provide values with 1, 2, or 3 total placeValue digits
+  // + Possible to get 0-9, 10-99, and 100-149
+  std::generate(array.begin(), array.end(), [](){ return rand() % 150;});
+
+  auto print = [](std::vector<int> array) {
+    for (const auto &i : array) {
+      std::cout << i << ", ";
+    }
+    std::cout << std::endl;
+  };
+
+  std::cout << "Unsorted array: \n";
+  print(array);
+
+  RadixSort(array);
+
+  std::cout << "Sorted array: \n";
+  print(array);
+}