#include <stdio.h>
int binSearch(int arr[], int low, int high, int key);
int binSearch2(int arr[], int low, int high, int key);
int binSearch3(int arr[],int start,int ends,int key);
int main() {
int arr[]={3,8,11,15,17,22,23,26,28,29,34};
//printf("%d",binSearch(arr,0,10,26));
printf("%d",binSearch3(arr,0,10,26));
return 1;
}
int binSearch(int arr[], int low, int high, int key) {
int flag=-1;
int mid = (low + high) / 2;
if (low > high) {
flag= -1;
} else {
if (arr[mid] < key) {
flag= binSearch(arr, mid + 1, high, key);
} else if (arr[mid]>key) {
//For example, the node you're looking for is at the bottom layer & NBSP; Then this layer will return to the subscript and catch it with a flag...
flag= binSearch(arr,low,mid-1,key);//I almost forgot to flag the catch return value again
} else {
flag= mid;
}
}
return flag;
}
//ok==============================
int binSearch2(int arr[], int low, int high, int key) {
int mid = (low + high) / 2;
if (low > high) {
return -1;
} else {
if (arr[mid] < key) {
return binSearch2(arr, mid + 1, high, key);
} else if (arr[mid]>key) {
return binSearch2(arr,low,mid-1,key);
} else {
return mid;
}
}
}
int binSearch3(int arr[],int start,int ends,int key){
int mid=-1;
while(start<=ends){
mid=(start+ends)/2;
if(arr[mid]<key){
start=mid+1;
}else if(arr[mid]>key){
ends=mid-1;
}else{
break;
}
}//The end of the above loop is not necessarily start> Ends of Because of the break statement
if(start>ends){
mid=-1;
}
return mid;
}