最近复习算法,为了年后找工作做准备,看了看网上归并排序,只懂算法原理源码没有看懂,算了,还是根据原理手撸吧!!!
如果大家想了解其他两种牛掰的排序,请猛戳下面链接
归并排序复杂度O(nlogn)
public class MergeSort {
public static int arr[] = {2,4,7,8,9,4,5,1,2,3,6,8,7,8,54,4,2,58,47,5,8,4,2,5};
public static void main(String[] args) {
sort(arr,0,arr.length-1); //排序
print(); //打印
}
//拆分
public static void sort(int left,int right){
if(left >= right)
return;
//递归终止条件,一个子数组只有一个或两个元素
if(right-left==1){
if(arr[left]>arr[right]){
int t = arr[left];
arr[left] = arr[right];
arr[right] = t;
}
return;
}
//递归分解
int mid = (left + right)/2;
sort(arr,left,mid);
sort(arr,mid+1,right);
//合并
merge(left,mid,right);
}
//合并
public static void merge(int left,int mid,int right){
int i = left;
int j = mid+1;
int k = 0;
//开辟临时数组,合并两个有序子数组
int temp[] = new int[right-left+1];
while(i<=mid && j<=right){
if(arr[i]<arr[j]){
temp[k++] = arr[i++];
}else{
temp[k++] = arr[j++];
}
}
while(i<=mid){
temp[k++] = arr[i++];
}
while(j<=right){
temp[k++] = arr[j++];
}
//将临时数组合并到原来数组中
k = 0;
for(i = left;i<=right;i++){
arr[i] = temp[k++];
}
}
/**
* 打印
*/
public static void print(){
for(int a:arr){
System.out.print(a+",");
}
System.out.println();
}
}
自己手撸的印象确实比看网上或看书来的深刻
结束,拜拜