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C# Program to Count number of binary strings without consecutive 1’s

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  • Last Updated : 16 Jun, 2022
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Given a positive integer N, count all possible distinct binary strings of length N such that there are no consecutive 1’s.

Examples:

Input:  N = 2
Output: 3
// The 3 strings are 00, 01, 10

Input: N = 3
Output: 5
// The 5 strings are 000, 001, 010, 100, 101

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C#




// C# program to count all distinct binary
// strings without two consecutive 1's
using System;
 
class Subset_sum {
    static int countStrings(int n)
    {
        int[] a = new int[n];
        int[] b = new int[n];
        a[0] = b[0] = 1;
        for (int i = 1; i < n; i++) {
            a[i] = a[i - 1] + b[i - 1];
            b[i] = a[i - 1];
        }
        return a[n - 1] + b[n - 1];
    }
 
    // Driver Code
    public static void Main()
    {
        Console.Write(countStrings(3));
    }
}
 
// This code is contributed by nitin mittal

Output:

5

Time Complexity: O(n)
Auxiliary Space: O(n)

Please refer complete article on Count number of binary strings without consecutive 1’s for more details!

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