public class BubbleSort {
	public static void bubbleSort(int[] a) {
		for (int j = 1; j < a.length; j++) {
			for (int i = 0; i < a.length - j; i++) {
				if (a[i] > a[i + 1]) {
					int temp = a[i];
					a[i] = a[i + 1];
					a[i + 1] = temp;
				}
			}
		}
	}
	public static void main(String[] args) {
		int a[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7, 2, 3, 0, 43, 23, 12, 4, 1, 15, 7,
				3, 8, 31 };
		bubbleSort(a);
		for(int i = 0; i < a.length; i++){
			System.out.print(a[i]+" ");
		}
	}
}

选择排序

public class SelectSort {
	public static void selectSort(int[] a) {
		int min;
		for (int i = 0; i < a.length - 1; i++) {
			min = i;
			for (int j = min + 1; j < a.length; j++) {
				if (a[min] > a[j]) {
					int temp = a[min];
					a[min] = a[j];
					a[j] = temp;
				}
			}
		}
	}

	public static void main(String[] args) {
		int a[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7,
				2, 3, 0, 43, 23, 12, 4, 1, 15, 7, 3, 8, 31 };
		selectSort(a);
		for (int i = 0; i < a.length; i++) {
			System.out.print(a[i] + " ");
		}
	}
}

插入排序

public class InsertSort {
	public static void insertSort(int[] a) {
		for (int i = 1; i < a.length; i++) {
			int key = a[i];
			int j = i - 1;
			while (j >= 0 && a[j] > key) {
				a[j+1] = a[j];
				j--;
			}
			a[j+1] = key;
		}
	}
	
	public static void main(String[] args) {
		int a[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7,
				2, 3, 0, 43, 23, 12, 4, 1, 15, 7, 3, 8, 31 };
		insertSort(a);
		for (int i = 0; i < a.length; i++) {
			System.out.print(a[i] + " ");
		}
	}
}

希尔排序

public class ShellSort {
	public static void shellSort(int[] a) {
		for (int gap = a.length / 2; gap > 0; gap /= 2)
			for (int i = gap; i < a.length; i++) {
				int key = a[i];
				int j = i - gap;
				while (j >= 0 && a[j] > key) {
					a[j + gap] = a[j];
					j -= gap;
				}
				a[j + gap] = key;
			}

	}

	public static void main(String[] args) {
		int a[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7,
				2, 3, 0, 43, 23, 12, 4, 1, 15, 7, 3, 8, 31 };
		shellSort(a);
		for (int i = 0; i < a.length; i++) {
			System.out.print(a[i] + " ");
		}
	}
}

快速排序

public class QuickSort {
	
	/*public static int partition(int[] a, int p, int r) {
		int x = a[r];
		int i = p - 1;
		for (int j = p; j < r; j++) {
			if (a[j] <= x) {//如果a[j]<x就将后面a[i]后面a[i+1](值大于x)与a[j](值<a[j])进行交换
				i++;
				
				int temp = a[i];
				a[i] = a[j];
				a[j] = temp;
				
			}
		}
		i++;
		int temp = a[i];
		a[i] = a[r];
		a[r] = temp;
		return i;
	}*/
	 
	public static int partition(int a[], int p, int r) {
		int x = a[p];
		int i = p;
		int j = r ;
		while (i < j) {
			while (a[j] >= x && i<j)
				j--;
			a[i] = a[j];//把小于X的那个数拿到前面的a【i】中
			while (a[i] <= x && i<j)
				i++;
			a[j] = a[i];//把大于X的那个数拿到后面的a【j】中
		}
		a[j] = x;//将X拿到分割处
		return j;
	}

	public static void quickSort(int[] a, int p, int r) {
		if (p < r) {
			int q = partition(a, p, r);
			quickSort(a, p, q-1);
			quickSort(a, q + 1, r);
		}
	}

	public static void main(String[] args) {
		int a[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7, 2, 3, 0, 43, 23, 12, 4, 1, 15, 7,
				3, 8, 31 };
		quickSort(a, 0, a.length-1);
		for (int i = 0; i < a.length; i++) {
			System.out.print(a[i] + " ");
		}

	}
}

合并排序

public class MergeSort {
	public static void merge(int A[], int p, int q, int r) {
		int[] L = new int[q - p + 1];
		int[] R = new int[r - q];
		for (int i = p, j = 0; i <= q; i++, j++) {
			L[j] = A[i];
		}
		for (int i = q + 1, j = 0; i <= r; i++, j++) {
			R[j] = A[i];
		}
		int pos = p;
		int i = 0, j = 0;
		for (; i < L.length && j < R.length;) {
			if (L[i] <= R[j]) {
				A[pos++] = L[i++];
			} else {
				A[pos++] = R[j++];
			}
		}
		if (i < L.length) {
			for (; i < L.length;)
				A[pos++] = L[i++];
		} else if (j < R.length) {
			for (; j < R.length;)
				A[pos++] = R[j++];
		}
	}

	public static void mergeSort(int[] A, int p, int r) {
		if (p < r) {
			int q = (p + r) / 2;
			mergeSort(A, p, q);
			mergeSort(A, q + 1, r);
			merge(A, p, q, r);
		}
	}

	public static void main(String[] args) {
		int A[] = { 5, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 2, 45, 7, 2, 4, 23, 7, 2, 3, 0, 43, 23, 12, 4, 1, 15, 7,
				3, 8, 31 };
		mergeSort(A, 0, A.length - 1);
		for (int i = 0; i < A.length; i++) {
			System.out.print(A[i] + " ");
		}
	}
}

堆排序

public class HeapSort {
	//求双亲位置
	static int parent(int i) {
		return i / 2;
	}
	//求左孩子位置
	static int left(int i) {
		return 2 * i;
	}
	//求右孩子位置
	static int right(int i) {
		return 2 * i + 1;
	}
	//维持大顶堆的性质
	static void maxHelpify(int[] A, int i) {
		int l = left(i);
		int r = right(i);
		int largest = 0;
		if (l <= A[0] && A[l] > A[i])
			largest = l;
		else
			largest = i;
		if (r <= A[0] && A[r] > A[largest])
			largest = r;
		if (largest != i) {
			int temp = A[largest];
			A[largest] = A[i];
			A[i] = temp;
			maxHelpify(A, largest);
		}
	}
	//建立大顶堆
	static void buildMaxHeap(int[] A){
		for(int i=(A.length-1)/2; i>0; i--){
			maxHelpify(A, i);
		}
	}
	//堆排序
	public static void heapSort(int[] A){
		buildMaxHeap(A);//建立大顶堆
		//每次把堆顶的数放到数组最后，然后把堆的大小减1，再次维持第一个数的大顶堆性质
		for(int i = A.length - 1; i>=2; i--){
			int temp = A[1];
			A[1] = A[i];
			A[i] = temp;
			A[0]--;
			maxHelpify(A, 1);
		}
	}
	public static void main(String[] args) {
		int A[] = new int[3];
		A[0] = A.length-1;//a[0]存放堆的大小
		for(int i = 1; i < A.length; i++){
			A[i] = (int) (Math.random()*10);
		}
		heapSort(A);
		for (int i = 1; i < A.length; i++) {
			System.out.print(A[i] + " ");
		}
	}
}

其他：还有一种计数排序。

比较简单：就是将数组下标作为元素的value,特殊情况下使用。如排序N个人的年龄就可以用计数排序。将年龄看作数组的下标，定义一个大小为100的数组，将年龄与之比较，如果年龄==下标就将，该下标的value+1.时间复杂度为（N）。