Implementation of binary search in C language

C Language to achieve binary search

Preface

​ Binary search is relatively simple , But still flowers 5 Minutes to write , It is convenient to be lazy in the future .

What is binary search

​ A binary search is a binary search , I believe everyone has played the game of guessing numbers , Each time you use dichotomy, you can guess the number with the least number of times .

​ Let's say there's an array ,A[10] = {11,12,13,14,15,16,17,18,19,20}.

​ Define three pointers ：low,mid,high. And the target number we're looking for goal.

​ At the beginning low Point to First element ,high Point to The last element , Every time mid=(low+high)/2, When the target value is mid On the right low=mid+1, When the target value is mid On the left high = mid -1. When low>high or A[mid]=goal when , Find the end .

Code implementation

#include<stdio.h>
#define N 10

int Binary_search(int A[],int low,int high,int goal,int *index)
{
    
	int mid; 
	while(low<=high)// When low>high Stop when 
	{
    
		mid = (low+high)/2;
		
		if(A[mid]==goal)
		{
    
			*index = mid;
			return *index;// If you have found , Return the subscript directly 
		}
	
		if(A[mid]<goal)// The target value is on the right , The pointer moves to the right 
			low = mid + 1;
		else 
			high = mid - 1;
	}
	return 0;
}

int main()
{
    
	int A[N] = {
    11,12,13,14,15,16,17,18,19,20};
	int index;
	if(Binary_search(A,0,N-1,20,&index))// Pass in the array separately ,low The pointer ,high The pointer , The target goal, And get the target value subscript 
		printf(" Already found ! Subscript to be ：%d\n",index);
	else
		printf(" To find the failure , The element may not exist !");
	
	return 0;
}

It has been tested .