归并排序
代码实现（java）:
public class MergeSort{
public static void mergeSort(int[] a, int sart, int end){
if(start >= end)
return;
int mid = start + (end - start) >> 1;
mergeSort(a, start, mid);
mergeSort(a, mid+1, end);
merge(a, start, mid, end);
}
public static void merge(int[] a, int start, int mid, int end){
int temp = new int[end - start + 1];
int i = start;
int j = mid + 1;
int k = 0;
while(i <= mid && j <= end){
if(a[i] < a[j])
temp[k++] = a[i++];
else
temp[k++] = a[j++];
}
while(i <= mid)
temp[k++] = a[i++];
while(j <= end)
temp[k++] = a[j++];
for(i = 0; i < k; i++){
a[start+i] = temp[i];
}
}
}
