Find the first element in a sorted array that is greater than the target

Question

In a general binary search, we are looking for a value which appears in the array. Sometimes, however, we need to find the first element which is either greater or less than

Answer 1

kind =0: exact match, kind=1: just grater than x, kind=-1: just smaller than x;

It returns -1 if no match is found.

#include 
#include 

using namespace std;


int g(int arr[], int l , int r, int x, int kind){
    switch(kind){
    case 0: // for exact match
        if(arr[l] == x) return l;
        else if(arr[r] == x) return r;
        else return -1;
        break;
    case 1: // for just greater than x
        if(arr[l]>=x) return l;
        else if(arr[r]>=x) return r;
        else return -1;
        break;
    case -1: // for just smaller than x
        if(arr[r]<=x) return r;
        else if(arr[l] <= x) return l;
        else return -1;
        break;
    default:
        cout <<"please give "kind" as 0, -1, 1 only" << ednl;
    }
}

int f(int arr[], int n, int l, int r, int x, int kind){
    if(l==r) return l;
    if(l>r) return -1;
    int m = l+(r-l)/2;
    while(m>l){
        if(arr[m] == x) return m;
        if(arr[m] > x) r = m;
        if(arr[m] < x) l = m;
        m = l+(r-l)/2;
    }
    int pos = g(arr, l, r, x, kind);
    return pos;
}

int main()
{
    int arr[] = {1,2,3,5,8,14, 22, 44, 55};
    int n = sizeof(arr)/sizeof(arr[0]);
    sort(arr, arr+n);
    int tcs;
    cin >> tcs;
    while(tcs--){
        int l = 0, r = n-1, x = 88, kind = -1; // you can modify these values
        cin >> x;
        int pos = f(arr, n, l, r, x, kind);
        // kind =0: exact match, kind=1: just grater than x, kind=-1: just smaller than x;
        cout <<"position"<< pos << " Value ";
        if(pos >= 0) cout << arr[pos];
        cout << endl;
    }
    return 0;
}