java实现归并排序模板
算法介绍
归并排序运用了递归的想法,又是分而治之,有“分”(将数组一分为二,分别排序两个子数组)和“治”(将子数组合并为目标数组)两部分,看代码就理解了。
代码模板
import java.util.Arrays;
import java.util.logging.LogRecord;
public class my {
public static void main(String []args){
int []arr = {
9,8,7,6,5,4,3,2,1};
sort(arr);
System.out.println(Arrays.toString(arr));
}
public static void sort(int []arr){
int []temp = new int[arr.length]; //创建一个临时数组来存排序过程中的结果
sort(arr,0,arr.length-1,temp);
}
public static void sort(int []arr, int left, int right, int []temp){
if (left < right){
mid = (left + right) /2;
sort(arr, left, mid, temp);
sort(arr, left, mid + 1, temp);
merge(arr, left, mid, right, temp);
}
}
public static void merge(int []arr, int left, int mid, int right, int []temp){
int i = left; //左边指针
int j = right; //右边指针
int t = 0; //temp数组指针
while(i <= mid && j <= right ){
if (arr[i] <= arr[j]){
temp[t++] = arr[i++];
}
else{
temp[t++] = arr[j++];
}
}
//将剩余的补到temp数组里
while(i <= mid){
temp[t++] = arr[i++];
}
while(j <= right){
temp[t++] = arr[j++];
}
}
}