Count 1’s in a sorted binary array in C++

In this tutorial, we will be discussing a program to find the 1’s in a sorted binary array.

For this we will be provided with an array containing only 1 and 0. Our task is to count the number of 1’s present in the array.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
//returning the count of 1
int countOnes(bool arr[], int low, int high){
   if (high >= low){
      int mid = low + (high - low)/2;
      if ( (mid == high || arr[mid+1] == 0) && (arr[mid] == 1))
         return mid+1;
      if (arr[mid] == 1)
         return countOnes(arr, (mid + 1), high);
      return countOnes(arr, low, (mid -1));
   }
   return 0;
}
int main(){
   bool arr[] = {1, 1, 1, 1, 0, 0, 0};
   int n = sizeof(arr)/sizeof(arr[0]);
   cout << "Count of 1's in given array is " << countOnes(arr, 0, n-1);
   return 0;
}

Output

Count of 1's in given array is 4

Ayush Gupta

Updated on 05-Feb-2020 07:32:28

• Related Questions & Answers
• Count Binary String without Consecutive 1's
• Count the number of 1’s and 0’s in a binary array using STL in C++
• Count subarrays consisting of only 0’s and only 1’s in a binary array in C++
• Find the index of first 1 in a sorted array of 0's and 1's in C++
• Count number of binary strings without consecutive 1's in C
• Absolute distinct count in a sorted array?
• Finding maximum number of consecutive 1's in a binary array in JavaScript
• Given a sorted array of 0’s and 1’s, find the transition point of the array in C++
• Absolute distinct count in a sorted array in C++?
• 1’s and 2’s complement of a Binary Number?
• Program to Count number of binary strings without consecutive 1’s in C/C++?
• Count number of binary strings of length N having only 0’s and 1’s in C++
• Count smaller elements in sorted array in C++
• C/C++ Program to Count number of binary strings without consecutive 1’s?
• Convert Sorted Array to Binary Search Tree in Python