[英]Quicksort C++ Implementation not working
我正在嘗試使quicksort用於整數數組,但是由於某種原因,它無法正確排序。
#include <conio.h>
#include <iostream>
#include <stdlib.h>
using namespace std;
int partition(int * arr, int left, int right, int index);
int quicksort(int * arr, int left, int right);
int main(void){
int arr[] = { 5,0,7,2,9,4,1,3,6,8 };
quicksort(arr, 0, 9);
for (int i = 0; i < 10; i++){
cout << arr[i] << std::endl;
}
}
int quicksort(int * arr, int left, int right){
int pivot = 0;
if (left < right){
pivot = partition(arr, left, right, pivot);
for (int i = left; i <= right; i++){
cout << arr[i] << " ";
}
cout << std::endl;
quicksort(arr, left, pivot - 1);
quicksort(arr, pivot + 1, right);
}
return 0;
}
int partition(int *arr, int left, int right, int index){
int pivotValue = arr[index];
int storedIndex = left;
int tmp;
tmp = arr[index];
arr[index] = arr[right];
arr[right] = tmp;
for (int i = left; i < right; i++){
if (arr[i]<= pivotValue){
tmp = arr[i];
arr[i] = arr[storedIndex];
arr[storedIndex] = tmp;
storedIndex++;
}
}
tmp = arr[storedIndex];
arr[storedIndex] = arr[right];
arr[right] = tmp;
return storedIndex;
}
我遵循了WikiPedia Quicksort上的算法,但仍然無法正常工作。 我究竟做錯了什么??
0 2 4 1 3 5 8 9 6 7
0 2 4 1 3
0 4 1 2
1 3 4
2 9 6 8
6 7 9
8 0 1 3 4 5 2 6 7 9
Press any key to continue . . .
您的數據透視元素始終是數組的第一個元素。 使用子數組調用quicksort或使用初始數據透視表索引調用它。 下面的代碼執行后者。
#include <iostream>
#include <stdlib.h>
using namespace std;
int partition(int *arr, int left, int right, int index);
int quicksort(int *arr, int left, int right, int pivot);
int main(void) {
int arr[] = {5, 0, 7, 2, 9, 4, 1, 3, 6, 8};
quicksort(arr, 0, 9, 0);
for (int i = 0; i < 10; i++) {
cout << arr[i] << std::endl;
}
}
int quicksort(int *arr, int left, int right, int pivot) {
//int pivot = 0;
if (left < right) {
pivot = partition(arr, left, right, pivot);
quicksort(arr, left, pivot - 1, left);
quicksort(arr, pivot + 1, right, pivot + 1);
}
return 0;
}
int partition(int *arr, int left, int right, int index) {
int pivotValue = arr[index];
int storedIndex = left;
int tmp;
tmp = arr[index];
arr[index] = arr[right];
arr[right] = tmp;
for (int i = left; i < right; i++) {
if (arr[i] <= pivotValue) {
tmp = arr[i];
arr[i] = arr[storedIndex];
arr[storedIndex] = tmp;
storedIndex++;
}
}
tmp = arr[storedIndex];
arr[storedIndex] = arr[right];
arr[right] = tmp;
return storedIndex;
}
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