testmergersort.java

学算法时写的程序了

package divide;

public class TestMergerSort {
	private static int[] a = {310,285,179,652,351,423,861,254,450,520};
	public static void mergeSort(int low,int high) {
		if(low < high) {
			int mid = (low + high) / 2;
			mergeSort(low,mid);
			mergeSort(mid + 1,high);
			merge(low,mid,high);
		}
	}
	
	public static void merge(int low,int mid,int high) {
		int[] b = new int[high-low+1];
		int left = low;
		int i = 0;
		int right = mid + 1;
		while(left <= mid && right <= high) {
			if(a[left] <= a[right]) {
				b[i++] = a[left++];
			}	else {
				b[i++] = a[right++];
			}
		}
		if(left > mid) {
			while(right <= high) {
				b[i++] = a[right++];
			}
		}
		if(right > high) {
			while(left <= mid) {
				b[i++] = a[left++];
			}
		}
		i = 0;
		for(int k = low;k <= high;k++) {
			a[k] = b[i++];
		}
	}
	
	public static void main(String[] args) {
		System.out.println("排序前：");
		for(int temp:a) {
			System.out.print(temp+"  ");
		}
		System.out.println("\n");
		mergeSort(0,a.length - 1);
		System.out.println("归并排序后：");
		for(int temp:a) {
			System.out.print(temp+"  ");
		}
	}
}