Why I got undefined in binary search??

Question

function binarysearch(){
var a=[1,2,3];

let start=0;

let end=a.length-1;

let mid=Math.floor(start+end /2); //1

let target=3;

while(start<end)
{
if(a[mid]==target){
return mid

}
else if(target>a[mid]){
start=mid+1
}
else {
end=mid-1
}

}

}

console.log(binarysearch())

Answer 1

Aniket Ganguly

Because you didn't return any value

Answer 2

Aniket Ganguly

Yes you have returned but what if that condition will not execute?

There is no guarantee that condition will execute?

Answer 3

Because you put the line

let mid=Math.floor((start+end)/2); //1

outside the while loop. So, mid is always same even after changing the start and end.

Just put that line just before the if statement inside the while loop and change the condition of while loop to start<=end (you have missed the = )

Answer 4

A͢J - S͟o͟l͟o͟H͟e͟l͟p͟e͟r͟ but I return mid in if statement see😀

Answer 5

Hmm

Answer 6

Your code inside else if is one what is executed. (You can place console.log() inside every if/else to find whats going on in your code. )
And inside this you dont return anything.

Answer 7

Initially, make sure that the array must be in ascending order
Then only we get the required output

It is the prerequisites of binary search