“二进制搜索”的 Function 无法正常工作

Question

When I Run my code And take input of array in ascending order from user the function which i have made runs and if the i search the middle number from array to find its location the code runs perfectly fine. But when i search the number from array which is not middle the code does not give me any output please fix this issue.

#include<iostream>
using namespace std;
 
void input_array(int arr[], int n);
int binary_search(int arr[], int n, int target);

int main()
{
     int limit;
    cout<<"Enter The Limit For An Array:- ";
    cin>>limit;

    int arr[limit];

    input_array(arr, limit);

    int target;

    cout<<"Enter The Number to find its position:- ";
    cin>>target;

    binary_search(arr, limit, target);

}

void input_array(int arr[], int n)
{
    cout<<"Enter The Number in Increasing Order "<<endl;

    for (int i = 0; i < n; i++)
    {
        cout<<i+1<<". Enter Number :- ";
        cin>>arr[i];
    }   
}

int binary_search(int arr[], int n, int target)
{
    int low = 0;
    int high = n-1;
    int mid;

    for (int i = 0; i < n; i++)
    {
        mid = (low+high) / 2;

        if (arr[mid] == target)
        {
            cout<<"The Position of The Given Target is :- "<<mid;
            return 0;
        }

        if (arr[mid] > target)
        {
            low = mid + 1;
        }
        
        else
        {
            high = mid - 1;
        }   
    }
    return -1;
}

i have created a program which is not working i dont know the reason why its not working kindly please solve my issue so i can proceed further.

Answer 1

Try this instead:

while (low + 1 < high)
{
    int mid = (low + high) / 2;
    if (arr[mid] >= target)
        low = mid;
    else
        high = mid;
}

if (arr[high] >= target)
    return high;
if (arr[low] >= target)
    return low;

return -1;

Answer 2

You were simply cycling N times, where N is the size of the array while with binary search it cycles at most log (N) times. In addition to a trivial problem of inverted logic. Below I show you the part of the code how it should be modified.

int binary_search(int arr[], int n, int target) {
    int low = 0;
    int high = n-1;
    int mid;

    while(low <= high) {
        mid = (low+high) / 2;

        if (arr[mid] == target) {
            cout << "The Position of The Given Target is :- " << mid;
            return 0;
        }else if (arr[mid] < target) {
            low = mid + 1;
        } else {
            high = mid - 1;
        }   
    }
    return -1;
}

I hope I was clear. Don't worry about asking for more information