/**
 * 快速排序
 * */
public class QuickSort{

	
	/**
	 * 遞迴一
	 * */
	public static void sort1(int[] arr, int start, int end) {
		if(start < end){
			//初始先將第一個值
			int pvoit = arr[start];
			int left = start;
			int right = end;
			System.out.println("===================================================================");
			while(left < right){
				System.out.println(" left=" + left + ", right=" + right + ", pvoit=" + pvoit);
				while(left < right && arr[right] >= pvoit){
					right --;
				}
				if(left < right){
					arr[left ++ ] = arr[right];
				}
				
				while(left < right && arr[left] <= pvoit){
					left ++ ;
				}
				if(left < right){
					arr[right --] = arr[left];
				}
				System.out.println(Arrays.toString(arr));
			}
			System.out.println("===================================================================");
			arr[left] = pvoit;
			sort1(arr, start, left - 1);
			sort1(arr, left + 1, end);
		}
	}
	
	/**
	 * 遞迴二
	 * */
	public static void sort2(int[] arr, int start, int end){
		if(start < end){
			int povit = RandomUtil.rangeRandom(start, end);
			int left = start;
			int right = end;
			while(left < right){
				while(left < right && left != povit && arr[left] <= arr[povit]){
					left ++ ;
				}
				if(left < right){
					swap(arr, left, povit);
					povit = left;
				}
				while(left < right && right != povit && arr[right] >= arr[povit]){
					right --;
				}
				if(left < right){
					swap(arr, right, povit);
					povit = right;
				}
			}
			
			sort2(arr, start, left - 1);
			sort2(arr, left + 1, end);
		}
	}
	
	/**
	 * 非遞迴實現快速排序
	 * */
	public static void sort3(int[] arr, int start, int end){
		if(start < end){
			Stack<Integer> startStack = new Stack<Integer>();
			Stack<Integer> endStack = new Stack<Integer>();
			
			startStack.push(start);
			endStack.push(end);
			
			while(startStack.size() > 0 && endStack.size() > 0){
				int tempStart = startStack.pop();
				int tempEnd = endStack.pop();
				if(tempStart < tempEnd){
					int povit = RandomUtil.rangeRandom(tempStart, tempEnd);
					int left = tempStart;
					int right = tempEnd;
					
					while(left < right){
						while(left < right && left != povit && arr[left] <= arr[povit]){
							left ++ ;
						}
						if(left < right){
							swap(arr, left, povit);
							povit = left;
						}
						while(left < right && right != povit && arr[right] >= arr[povit]){
							right --;
						}
						if(left < right){
							swap(arr, right, povit);
							povit = right;
						}
					}
					startStack.push(tempStart);
					startStack.push(left + 1);
					endStack.push(left - 1);
					endStack.push(tempEnd);
				}
			}
		}
	}
	
	public static void swap(int[] arr, int i, int j){
		if(arr != null && i != j){
			int temp = arr[i];
			arr[i] = arr[j];
			arr[j] = temp;
		}
	}
	
	public static void main(String[] args) {
		int[] arr = {2, 1,6,3,4,11,2,3,5,6};
		sort3(arr, 0, arr.length-1);
		
		System.out.println(Arrays.toString(arr));
	}
}