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Merge.java
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50 lines (31 loc) · 989 Bytes
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package com.mytest.algorithm.sort;
import com.mytest.algorithm.util.Util;
/**
* @author wangyujiang
* 自顶向下的归并排序
* 将二个子数组排序，通过归并将二个子数组来将整个数组排序
*/
public class Merge {
//原地归并
public static void merge(Comparable[] a, int lo, int mid, int hi) {
int i = lo, j = mid+1;
Comparable[] aux = new Comparable[a.length];
//复制新数组
for(int k=0; k < a.length; k++)
aux[k] = a[k];
//将二个子数组aux[lo,...,mid],aux[j,...,hi]归并到数组a中
for (int k=lo; k <= hi; k++){
if (i > mid) a[k] = aux[j++];
else if (j > hi) a[k] = aux[i++];
else if (Util.less(aux[i],aux[j])) a[k] = aux[i++];
else a[k] = aux[j++];
}
}
public static void sort(Comparable[] a, int lo, int hi) {
if (lo >= hi) return;//排序结束
int mid = lo + (hi-lo)/2;
sort(a,lo,mid);//左半边排序
sort(a,mid+1,hi);//右半边排序
merge(a,lo,mid,hi);//左右归并
}
}