- Trending Categories
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 consecutive 1s of length >= n in binary representation of a number in C++
Suppose, we have two integers x and n, our task is to search for the first consecutive stream of 1s (32-bit binary) which is greater than or equal to the value of n in length and return its position. If no such string exists, then return -1. For example, if x = 35, and n = 2, then result will be 31. The binary representation of 35 in a 32-bit integer is like −
00000000000000000000000000100011. So two consecutive 1s are present at index 31, so the answer is 31.
To solve this problem, we have to find the number of leading zeros, and from that count, we will try to find the consecutive 1s. Let us see the example to get a better idea.
Example
#include<iostream> using namespace std; int leadingZeroCount(int x) { unsigned y; int n; n = 32; for(int i = 16; i > 1; i = i/2 ){ y = x >> i; if(y != 0){ n -= i; x = y; } } y = x >> 1; if (y != 0) return n - 2; return n - x; } int consecutiveOnePosition(unsigned x, int n) { int k, p; p = 0; while (x != 0) { k = leadingZeroCount(x); x = x << k; p = p + k; k = leadingZeroCount(~x); if (k >= n) return p + 1; x = x << k; p = p + k; } return -1; } int main() { int x = 35; int n = 2; cout << "Consecutive 1s of length " << n << " is starting from index: " << consecutiveOnePosition(x, n); }
Output
Consecutive 1s of length 2 is starting from index: 31
Advertisements