Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Find the index of first 1 in a sorted array of 0's and 1's in C++
In this problem, we are given an array bin[] consisting of boolean values (only 0's and 1's) in sorted order. Our task is to find the index of first 1 in a sorted array of 0's and 1's.
Let's take an example to understand the problem,
Input : bin[] = {0, 0, 0, 1, 1}
Output : 3Explanation −
First 1 of the binary array is encountered at index 3.
Solution Approach
To solve the problem, we basically need to find the index of 1st 1 in the array. For that we can use a searching technique.
One approach can be using linear search, we will traverse the array from index 0 to the end of array. And return the index of first 1 in the array, otherwise print -1.
Example
Program to illustrate the working of our solution
#include <iostream>
using namespace std;
double find1stOneInArray(int bin[], int n) {
for (int i = 0; i < n; i++)
if (bin[i] == 1)
return i;
return -1;
}
int main() {
int bin[] = { 0, 0, 0, 1, 1, 1 };
int n = sizeof(bin) / sizeof(bin[0]);
cout<<"The index of 1st occurrence of 1 in array is "<<find1stOneInArray(bin,n);
return 0;
}Output
The index of 1st occurrence of 1 in array is 3
Another searching technique that can be used is binary search as the array is sorted.
Example
Program to illustrate the working of our solution
#include <iostream>
using namespace std;
double find1stOneInArray(int bin[], int n) {
int low = 0;
int high = (n - 1);
int mid;
while (low <= high) {
mid = (low + high) / 2;
if (bin[mid] == 1 && (mid == 0 || bin[mid - 1] == 0))
return mid;
else if (bin[mid] == 1)
high = mid - 1;
else
low = mid + 1;
}
return -1;
}
int main() {
int bin[] = { 0, 0, 0, 1, 1, 1, 1 };
int n = sizeof(bin) / sizeof(bin[0]);
cout<<"The index of 1st occurrence of 1 in array is "<<find1stOneInArray(bin,n);
return 0;
}Output
The index of 1st occurrence of 1 in array is 3
Updated on: 28-Jan-2022
355 Views
Advertisements