快排

快速排序時間複雜度爲O(nlogn)

有關於快排的動畫演示

代碼

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
using namespace std;

void qsort (int *arr, int left, int right) {
	if (left < right) {
		int key = arr[left];
		int low = left, high = right;
		while (low < high) {
			for (;low < high && arr[high] > key;high--);
			arr[low] = arr[high];
			for (;low < high && arr[low] < key;low++);
			arr[high] = arr[low];
		}
		arr[low] = key;
		qsort (arr, left, low-1);
		qsort (arr, low+1, right);
	}
}

int main (void) {
	int num;
	int arr[100];
	while (scanf ("%d", &num) != EOF) {
		for (int i = 0;i < num;i++) {
			scanf ("%d", &arr[i]);
		}
		
		qsort (arr, 0, num-1);
		
		for (int i = 0;i < num;i++) {
			printf ("%d ", arr[i]);
		}
		printf ("\n");
	}
	return 0;
}