归并排序

package sort;
//归并排序
public class MergeSortTest {
    public static void main(String[] args){
        int[] data = new int[]{5, 3, 6, 2, 1, 9, 4, 8, 7};
        mergeSort(data);
        System.out.println("排序后的数组：");
        print(data);
    }
    
    public static void mergeSort(int[] data){
        sort(data, 0, data.length-1);
    }
    
    public static void sort(int[] data, int left, int right){
        if (left >= right)
            return;
        int center  = (left + right) / 2;
        sort(data, left, center);
        sort(data, center+1, right);
        merge(data, left, center, right);
        print(data);
    }
    
    public static void merge(int[] data, int left, int center, int right){
        //临时数组
        int[] tempArr = new int[data.length];
        //右边数组的第一个元素索引
        int mid = center + 1;
        //tempIndex记录临时数组的索引
        int tempIndex = left;
        //缓存左数组的第一个元素的索引
        int tmp = left;
        
        while(left <= center && mid <=right){
            if (data[left] <= data[mid]){
                tempArr[tempIndex++] = data[left++];
            }else{
                tempArr[tempIndex++] = data[mid++];
            }
        }
        
        //剩余部分依次放入临时数组(实际上两个while只会执行其中一个)
        while (mid <= right){
            tempArr[tempIndex++] = data[mid++];
        }
        
        while (left <= center){
            tempArr[tempIndex++] = data[left++];
        }
        
        //将临时数组中的内容拷贝回原数组中
        while (tmp <= right){
            data[tmp] = tempArr[tmp++];
        }
    }
    
    public static void print(int[] data){
        for(int i=0; i<data.length; i++){
            System.out.print(data[i]+" ");
        }
        System.out.println();
    }
}