编辑代码

public class Test2 {
public static void main(String[] args) {
int[]arr=new int[]{1,2,3,4,5,6,7,8,9,10}; int num=3;
int index = isFind(arr, num); if(index==-1){
system.out.printIn(num+"不存在");}else{
System.out.println(num+"案引为:"+index);}
int num2=20;
int index2 = isFind(arr, num2); if(index2==-1){
System.out.println(num2+"不存在");}else{
System.out.println(num2+"索引为:"+index);

}
public static int isFind(int[] arr,int num){
for (int i = 0; i <arr.length; i++){
if(arr[i]==num){
return i;}
return -1;}

时间复杂度:0(n)