常用排序算法C++实现(堆排序,快速排序,归并排序,基数排序)
2015-11-30 12:40
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#include <iostream> #include <cstdlib> #include <ctime> #include <algorithm> using namespace std; const int ARR_COUNT = 5; const int SIZE = 18; const int RANGE = 1000; int arr[6][SIZE]; /* * heapSort, quickSort, mergeSort, radixSort */ /* * common */ void mySwap(int& a, int&b) { int temp = a; a = b; b = temp; } void printArr(const int arr[], const int size) { cout << "[ "; for (int i = 0; i < size; ++i) cout << arr[i] << " "; cout << "]" << endl; } /* * heap sort */ void balanceMaxHeap(int arr[], const int i, const int size) { if (i * 2 < size) { //has child int maxValIndex = i; if (arr[i * 2] > arr[maxValIndex]) maxValIndex = i * 2; if (i * 2 + 1 < size && arr[i * 2 + 1] > arr[maxValIndex]) maxValIndex = i * 2 + 1; if (maxValIndex != i) { mySwap(arr[i], arr[maxValIndex]); balanceMaxHeap(arr, maxValIndex, size); } } } void buildMaxHeap(int arr[], const int size) { for (int i = size - 1; i >= 0; --i) { //build heap balanceMaxHeap(arr, i, size); } } void heapSort(int arr[], const int size) { buildMaxHeap(arr, size); for (int i = 0; i < size; ++i) { //pop mySwap(arr[0], arr[size - 1 - i]); balanceMaxHeap(arr, 0, size - 1 - i); } } /* * quick sort */ int partition(int arr[], const int start, const int end) { int i = start + rand() * (end - start) / (RAND_MAX + 1); mySwap(arr[i], arr[end - 1]); //swap with last element int pos = start; for (int i = start; i < end - 1; ++i) { if (arr[i] < arr[end - 1]) mySwap(arr[pos++], arr[i]); } mySwap(arr[pos], arr[end - 1]); return pos; } void quickSortCore(int arr[], const int start, const int end) { //[start, end) if (start + 1 < end) { //at least two elements int mid = partition(arr, start, end); quickSortCore(arr, start, mid); quickSortCore(arr, mid + 1, end); } } void quickSort(int arr[], const int size) { quickSortCore(arr, 0, size); } /* * merge sort */ void mergeSortCore(int arr[], const int start, const int end) { //[start, end) if (start + 1 < end) { //at least two elements int mid = start + (end - start) / 2; mergeSortCore(arr, start, mid); mergeSortCore(arr, mid, end); //merge int start1 = start, start2 = mid; int* mergeArr = new int[end - start]; int mergeArrStart = 0; while (start1 < mid && start2 < end) { if (arr[start1] <= arr[start2]) mergeArr[mergeArrStart++] = arr[start1++]; else mergeArr[mergeArrStart++] = arr[start2++]; } while (start1 < mid) mergeArr[mergeArrStart++] = arr[start1++]; while (start2 < end) mergeArr[mergeArrStart++] = arr[start2++]; memcpy(arr + start, mergeArr, sizeof(int) * (end - start)); delete[] mergeArr; } } void mergeSort(int arr[], const int size) { mergeSortCore(arr, 0, size); } /* * radix sort, only effective for uint32_t */ void radixSortCore(int arr[], int temp[], const int size, const int offset) { const int mask = 0xFF; int cnt[256] = { 0 }; for (int i = 0; i < size; ++i) cnt[(arr[i] >> offset) & mask]++; for (int i = 1; i < 256; ++i) cnt[i] += cnt[i - 1]; for (int i = size - 1; i >= 0; --i) temp[--cnt[(arr[i] >> offset) & mask]] = arr[i]; } void radixSort(int arr[], const int size) { int* temp = new int[size]; radixSortCore(arr, temp, size, 0); radixSortCore(temp, arr, size, 8); radixSortCore(arr, temp, size, 16); radixSortCore(temp, arr, size, 24); delete[] temp; } int main() { srand((unsigned int)time(NULL)); for (int i = 0; i < SIZE; ++i) arr[0][i] = rand() * RANGE / (RAND_MAX + 1); for (int i = 1; i < ARR_COUNT; ++i) memcpy(arr[i], arr[0], sizeof(arr[0])); cout << "Original array:" << endl; for (int i = 0; i < ARR_COUNT; ++i) printArr(arr[i], SIZE); sort(arr[0], arr[0] + SIZE); heapSort(arr[1], SIZE); quickSort(arr[2], SIZE); mergeSort(arr[3], SIZE); radixSort(arr[4], SIZE); cout << "After sorting:" << endl; for (int i = 0; i < ARR_COUNT; ++i) printArr(arr[i], SIZE); return 0; }
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