排序（希尔、 堆 归并 快速）

排序（希尔排序  堆排序   归并 排序，  快速排序）

-------------------学习笔记

希尔排序：

		int temp;
		int gab = num.length;
		do{
			gab  = gab / 3 + 1;
			for (int i=gab; i <num.length; i++){
				temp = num[i];
				int j;
				for (j=i-gab; j>=0 && num[j] > temp; j-=gab){
					num[j+gab] = num[j];
				}
				num[j+gab] = temp;
			}
		}while (gab > 1);

堆排序：

	public static void main(String[] args) {
		int num[] = new int[]{9,8,7,6,5,4,3,2,1};
		int length = num.length;
		
		for (int i=length/2; i>=0; i--){
			HeapAdjust(num, i, length);
		}
		for (int i=length-1; i>0; i--){
			swap(num, 0, i);
			HeapAdjust(num, 0, i);
		}

		//for (int num1 : num)
			//System.out.println(num1);
	}
	
	private static void swap(int num[], int x, int y){
		int temp = num[x];
		num[x] = num[y];
		num[y] = temp;
	}
	private static void HeapAdjust(int num[], int s, int m){
		int temp = num[s];
		for (int j=2*s+1; j<m; j=2*s+1){
			if (j <m-1 && num[j] < num[j+1])
				j++;
			if (num[j] < temp)
				break;
			num[s] = num[j];
			s = j;
		}
		num[s] = temp;
	}

归并排序：

public class mergeSort {
	int[] arr;
	
	private void merge(int low, int mid, int high){
		int[] temp = new int[high - low + 1];
		int i = low, j = mid+1;
		int k = 0;
		while (i <= mid && j <= high){
			if (arr[i] < arr[j]){
				temp[k++] = arr[i++];
			}else{
				temp[k++] = arr[j++];
			}
		}
		while (i <= mid){
			temp[k++] = arr[i++];
		}
		while (j <= high){
			temp[k++] = arr[j++];
		}
		for (i=0; i<=high-low; i++){
			arr[i+low] = temp[i];
		}
	}
	private void sort(int low, int high){
		int mid = (low + high) / 2;
		if (low < high){
			sort(low, mid);
			sort(mid+1, high);
			merge(low, mid, high);
		}
		return;
	}
	public mergeSort(int[] arr1){
		arr = arr1;
		sort(0, arr.length-1);
	}
}

快速排序：

public class QuickSort {
	private int[] arr;
	private void swap(int x, int y){
		int temp = arr[x];
		arr[x] = arr[y];
		arr[y] = temp;
	}
	private void QuickSortRecursive(int start, int end){
		if (start >= end)
			return;
		int pivotkey = arr[end];
		int left = start;
		int right = end - 1;	
		while (left < right){
			while(arr[left] < pivotkey && left < right)
				left++;
			while(arr[right] >= pivotkey && left < right)
				right--;
			swap(left, right);
		}
		if (arr[left] >= pivotkey)
			swap(left, end);
		else
			left++;
		QuickSortRecursive(start, left-1);
		QuickSortRecursive(left+1, end);
	}
	public void sort(){
		QuickSortRecursive( 0, arr.length -1);
	}
	public QuickSort(int[] arr1){
		arr =  arr1;
	}	
}

优化：

public class QuickSort {
	private int[] arr;
	private final int maxSize = 7; 
	private void swap(int x, int y){
		int temp = arr[x];
		
		arr[x] = arr[y];
		arr[y] = temp;
	}
	private void median(int start, int end ){
		int mid  = (start - end) /2 + end;
		if (arr[start] > arr[end]){
			swap(start, end);		
		if (arr[start] > arr[mid])
			swap(start, mid);
		if (arr[mid] < arr[end])
			swap(mid, end);
		}
	}
	private void insertSort(int start, int end){
		int temp, j;
		for (int i=start+1; i<=end; i++){
			temp = arr[i];
			for (j =i;j>start && arr[j-1] > temp; j--){
					arr[j] = arr[j-1];
			}
			arr[j] = temp;
		}
	}
	private void QuickSortRecursive(int start, int end){
		if (maxSize <(start - end)){
			median(start, end);
			int pivotkey = arr[end];
			int left = start;
			int right = end - 1;	
			while (left < right){
				while(arr[left] < pivotkey && left < right)
					left++;
				while(arr[right] >= pivotkey && left < right)
					right--;
				swap(left, right);
			}
			if (arr[left] >= pivotkey)
				swap(left, end);
			else
				left++;
			QuickSortRecursive(start, left-1);
			QuickSortRecursive(left+1, end);
		}
		else
			insertSort(start, end);
			
	}
		public QuickSort(int[] arr1){
			arr =  arr1;
			QuickSortRecursive( 0, arr.length -1);
	}
	
}