50 lines
2.0 KiB
C++
50 lines
2.0 KiB
C++
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/*#############################################################################
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## Author: Shaun Reed ##
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## Legal: All Content (c) 2021 Shaun Reed, all rights reserved ##
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## About: An example implementation of counting sort using a custom library ##
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## ##
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## Contact: shaunrd0@gmail.com | URL: www.shaunreed.com | GitHub: shaunrd0 ##
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###############################################################################
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*/
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#include "lib-counting.hpp"
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#include <algorithm>
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#include <cstdint>
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#include <vector>
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void CountingSort(std::vector<int> &array)
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{
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std::vector<int> sortedArray(ARRAY_LENGTH);
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// Find the maximum value within the array to sort
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int32_t maxValue = INT32_MIN;
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for (const auto &val : array) maxValue = (val > maxValue) ? val : maxValue;
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// Create an array with element for all *values* within the range of the set
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// + Not the size of the array to sort, but instead a element of
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// + tempArray[val] = 0; for each val within the array we want to sort
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// Add one to maxValue to make up for zero index; 0's are possible, too!
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std::vector<int> tempArray(maxValue + 1, 0);
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// Count the occurrences of each value within the array to sort
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// + Store the end result as tempArray[value] = count;
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for (const auto &val : array) tempArray[val] += 1;
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// Count the values less than or equal to each element of tempArray
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// + Since each element stores its own count, just add the count at index i-1
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for (size_t i = 1; i <= maxValue; i++) {
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tempArray[i] += tempArray[i - 1];
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}
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for (ssize_t arrayIndex = array.size() - 1; arrayIndex >= 0; arrayIndex--) {
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// Store as references; Changes reflect on actual values within each array
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const int &arrayValue = array[arrayIndex];
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int &valueCount = tempArray[arrayValue];
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sortedArray[valueCount - 1] = arrayValue;
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valueCount = valueCount - 1;
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}
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array = sortedArray;
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}
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