为什么快速分类真的很慢？ 新的数组排序方法

• 按选择排序
• 合并排序
• 插入排序

int* glue(int* a, int lenA, int* b, int lenB) { int lenC = lenA + lenB; int* c = new int[lenC]; //   int indx_a = 0; int indx_b = 0; int i = 0; for (; i < lenC; ++i) { if (indx_a < lenA) { if (indx_b < lenB) { //     c[i] = (a[indx_a] < b[indx_b]) ? a[indx_a++] : b[indx_b++]; continue; } //      while (indx_a < lenA) c[i++] = a[indx_a++]; } else //      while (indx_b < lenB) c[i++] = b[indx_b++]; break; } return c; } 

 void glueDelete(int*& arr, int*& a, int lenA, int*& b, int lenB) { if (lenA == 0) { //    delete[] a; //     arr = b; //     return; } if (lenB == 0) { //    delete[] b; //     arr = a; //     return; } int *copy = glue(a, lenA, b, lenB); //  delete[]a; //    delete[]b; //    arr = copy; //   } 

 void insertionSort(int*& arr, int lo, int hi) { for (int i = lo + 1; i <= hi; ++i) for (int j = i; j > 0 && arr[j - 1] > arr[j]; --j) swap(arr[j - 1], arr[j]); } 

 void FirstNewGeneratingSort(int*& arr, int len) { if (len < 2) return; int* selection = new int[len << 1]; int left = len - 1; int right = len; int* restElements = new int[len]; int restLen = 0; if (arr[0] > arr[1]) swap(arr[0], arr[1]); selection[left--] = arr[0]; selection[right++] = arr[1]; for (int i = 2; i < len; ++i) { if (selection[right - 1] <= arr[i]) //     { selection[right++] = arr[i]; continue; } if (selection[left + 1] >= arr[i]) //     { selection[left--] = arr[i]; continue; } restElements[restLen++] = arr[i]; //      ,    } int selectionLen = right - left - 1; //   int* copy = glue(selection + left + 1, selectionLen, nullptr, 0); //       delete[] selection; //   2 * len ,          ,     selection = copy; //  ,    selection     delete[] arr; //    ,         ,       FirstNewGeneratingSort(restElements, restLen); glueDelete(arr, selection, selectionLen, restElements, restLen); } 

 void newGenerationMergeSort(int* a, int lo, int hi, int& minPortion) { if (hi <= lo) return; int mid = lo + (hi - lo) / 2; if (hi - lo <= minPortion) { //       ,     int* part = glue(a + lo, hi - lo + 1, nullptr, 0); //    FirstNewGeneratingSort(part, hi - lo + 1); for (int i = lo; i <= hi; ++i) { a[i] = part[i - lo]; } delete[] part; return; } newGenerationMergeSort(a, lo, mid, minPortion); newGenerationMergeSort(a, mid + 1, hi, minPortion); int* b = glue(a + lo, mid - lo + 1, a + mid + 1, hi - mid); for (int i = lo; i <= hi; i++) a[i] = b[i - lo]; delete[] b; } 

 /// works only if arr is pointer assigned by new keyword void newGenerationSort(int*& arr, int len) { int localCatchUp = min(catchUp, len); //            insertionSort(arr, 0, localCatchUp - 1); //     localCatchUp  if (len <= localCatchUp) //       n <= catchUp  return; //      int* selection = new int[len << 1]; //     new int[len * 2] int left = len - 1; //       int right = len; //       selection[left--] = arr[0]; for (int i = 1; i < localCatchUp; ++i) { selection[right++] = arr[i]; } int restLen = len >> 1; int* restFirst = new int[restLen]; int* restSecond = new int[restLen]; int restFirstLen = 0; int restSecondLen = 0; for (int i = localCatchUp; i < len; ++i) { if (selection[right - localCatchUp] <= arr[i]) { selection[right] = arr[i]; for (int j = right; selection[j - 1] > selection[j]; --j) swap(selection[j - 1], selection[j]); ++right; continue; } if (selection[left + localCatchUp] >= arr[i]) { selection[left] = arr[i]; for (int j = left; selection[j] >= selection[j + 1]; ++j) swap(selection[j], selection[j + 1]); --left; continue; } if (i & 1) { // i -  restFirst[restFirstLen++] = arr[i]; } else { restSecond[restSecondLen++] = arr[i]; } } delete[] arr; int selectionLen = right - left - 1; //     int* copy = glue(selection + left + 1, selectionLen, nullptr, 0); //        delete[] selection; //    2 * len   selection = copy; //      ,   newGenerationSort(restFirst, restFirstLen); newGenerationSort(restSecond, restSecondLen); int* part2; int part2Len; if (selectionLen < restFirstLen) { glueDelete(selection, restFirst, restFirstLen, selection, selectionLen); // selection += restFirst selectionLen += restFirstLen; part2 = restSecond; part2Len = restSecondLen; } else { glueDelete(part2, restFirst, restFirstLen, restSecond, restSecondLen); // part2 = restFirst + restSecond part2Len = restFirstLen + restSecondLen; } glueDelete(arr, selection, selectionLen, part2, part2Len); } 

 #include <iostream> #include <ctime> #include <vector> #include <algorithm> #include "time_utilities.h" #include "sort_utilities.h" using namespace std; using namespace rela589n; void printArr(int* arr, int len) { for (int i = 0; i < len; ++i) { cout << arr[i] << " "; } cout << endl; } bool arraysEqual(int* arr1, int* arr2, int len) { for (int i = 0; i < len; ++i) { if (arr1[i] != arr2[i]) { return false; } } return true; } int* createArray(int length) { int* a1 = new int[length]; for (int i = 0; i < length; i++) { a1[i] = rand(); //a1[i] = (i + 1) % (length / 4); } return a1; } int* array_copy(int* arr, int length) { int* a2 = new int[length]; for (int i = 0; i < length; i++) { a2[i] = arr[i]; } return a2; } void tester(int tests, int length) { double t1, t2; int** arrays1 = new int* [tests]; int** arrays2 = new int* [tests]; for (int t = 0; t < tests; ++t) { //    int* arr1 = createArray(length); arrays1[t] = arr1; arrays2[t] = array_copy(arr1, length); } t1 = getCPUTime(); for (int t = 0; t < tests; ++t) { quickSort(arrays1[t], 0, length - 1); } t2 = getCPUTime(); cout << "Avg Qsort time for " << length << " elements: " << (t2 - t1) * 1000 / tests << endl; int portion = catchUp = 8; t1 = getCPUTime(); for (int t = 0; t < tests; ++t) { newGenerationSort(arrays2[t], length); } t2 = getCPUTime(); cout << "Avg newGenSort time for " << length << " elements: " << (t2 - t1) * 1000 / tests //<< " Catch up coef: "<< portion << endl; bool confirmed = true; //     for (int t = 0; t < tests; ++t) { if (!arraysEqual(arrays1[t], arrays2[t], length)) { confirmed = false; break; } } if (confirmed) { cout << "Confirmed" << endl; } else { cout << "Review your code! Something wrong..." << endl; } } int main() { srand(time(NULL)); int length; double t1, t2; cout << "size: "; cin >> length; int t; cout << "tests: "; cin >> t; tester(t, length); system("pause"); return 0; } 

一句话：我使用了quickSort的这种特定实现，以便一切都是诚实的。 尽管算法库中的标准排序是通用的，但它的工作速度比下面介绍的慢2倍。

 // [min, max] int random(int min, int max) { return min + rand() % ((max + 1) - min); } void quickSort(int * arr, int b, int e) { int l = b, r = e; int piv = arr[random(l, r)]; while (l <= r) { for (; arr[l] < piv; ++l); for (; arr[r] > piv; --r); if (l <= r) swap(arr[l++], arr[r--]); } if (b < r) quickSort(arr, b, r); if (e > l) quickSort(arr, l, e); } 

 #pragma once #if defined(_WIN32) #include <Windows.h> #elif defined(__unix__) || defined(__unix) || defined(unix) || (defined(__APPLE__) && defined(__MACH__)) #include <unistd.h> #include <sys/resource.h> #include <sys/times.h> #include <time.h> #else #error "Unable to define getCPUTime( ) for an unknown OS." #endif /** * Returns the amount of CPU time used by the current process, * in seconds, or -1.0 if an error occurred. */ double getCPUTime() { #if defined(_WIN32) /* Windows -------------------------------------------------- */ FILETIME createTime; FILETIME exitTime; FILETIME kernelTime; FILETIME userTime; if (GetProcessTimes(GetCurrentProcess(), &create;Time, &exit;Time, &kernel;Time, &user;Time) != -1) { SYSTEMTIME userSystemTime; if (FileTimeToSystemTime(&user;Time, &user;SystemTime) != -1) return (double)userSystemTime.wHour * 3600.0 + (double)userSystemTime.wMinute * 60.0 + (double)userSystemTime.wSecond + (double)userSystemTime.wMilliseconds / 1000.0; } #elif defined(__unix__) || defined(__unix) || defined(unix) || (defined(__APPLE__) && defined(__MACH__)) /* AIX, BSD, Cygwin, HP-UX, Linux, OSX, and Solaris --------- */ #if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0) /* Prefer high-res POSIX timers, when available. */ { clockid_t id; struct timespec ts; #if _POSIX_CPUTIME > 0 /* Clock ids vary by OS. Query the id, if possible. */ if (clock_getcpuclockid(0, &id;) == -1) #endif #if defined(CLOCK_PROCESS_CPUTIME_ID) /* Use known clock id for AIX, Linux, or Solaris. */ id = CLOCK_PROCESS_CPUTIME_ID; #elif defined(CLOCK_VIRTUAL) /* Use known clock id for BSD or HP-UX. */ id = CLOCK_VIRTUAL; #else id = (clockid_t)-1; #endif if (id != (clockid_t)-1 && clock_gettime(id, &ts;) != -1) return (double)ts.tv_sec + (double)ts.tv_nsec / 1000000000.0; } #endif #if defined(RUSAGE_SELF) { struct rusage rusage; if (getrusage(RUSAGE_SELF, &rusage;) != -1) return (double)rusage.ru_utime.tv_sec + (double)rusage.ru_utime.tv_usec / 1000000.0; } #endif #if defined(_SC_CLK_TCK) { const double ticks = (double)sysconf(_SC_CLK_TCK); struct tms tms; if (times(&tms;) != (clock_t)-1) return (double)tms.tms_utime / ticks; } #endif #if defined(CLOCKS_PER_SEC) { clock_t cl = clock(); if (cl != (clock_t)-1) return (double)cl / (double)CLOCKS_PER_SEC; } #endif #endif return -1; /* Failed. */ } 

 a1[i] = rand(); 

 a1[i] = (i + 1) % (length / 4); 

 a1[i] = (i + 1);