Java作业杨枝10.28/10.29

package org.westor.daxiaochuan;
/*
* 一 .兔子生兔子问题
*
*
* */
public class Rabbit {
public static void main(String[] args){
int i=sum(20);
System.out.println("第20月:"+i+"只");

}
static  int sum(int i){
if(i==1||i==2){
return 1;
}else
{
return sum(i-1)+sum(i-2);
}
}
}

package org.binsearch;
/*
*
* 二    二分查找法
* */

public class BinSearch {

public static void main(String[] args){

int[] arr={13,24,57,69,80};
int index=binSearch(arr,0,arr.length-1,24);

System.out.println("24对应的索引为："+index);

}
//递归思想的二分查找功能
public static int binSearch(int arr[],int low,int high,int x ){
while(low<=high){
int mid=(low+high)/2;
if(x==arr[mid]){
return mid;
}else if(x<arr[mid]){
return binSearch(arr,low,mid-1,x);
}else{
return binSearch(arr,mid+1,high,x);
}

}
return -1;
}
}

package org.westor.daxiaochuan;
/**
* 3:统计大串中小串出现的次数
举例：在字符串” woaijavawozhenaijavawozhendeaijavawozhendehenaijavaxinbuxinwoaijavagun”中java出
现了5次
*
* */
public class DaChuan {
public static void main(String[] args){
String s="woaijavawozhenaijavawozhendeaijavawozhendehenaijavaxinbuxinwoaijavagun";
String s1="java";

int num=getNum(s,s1);
System.out.println("小串java在大串中出现的次数为："+num);

}

public static int getNum(String s,String s1){
int index=s.indexOf(s1);
int num=0;
while(index!=-1){
num++;
int newIndex=index+s1.length();
s=s.substring(newIndex);
index=s.indexOf(s1);
}

return num;

}
}