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1-bit and 2-bit Characters - Array - Easy - LeetCode - MiniTV

1-bit and 2-bit Characters - Array - Easy - LeetCode - मिनी टीवी

We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11).

Now given a string represented by several bits. Return whether the last character must be a one-bit character or not. The given string will always end with a zero.

Example 1:
Input: 
bits = [1, 0, 0]
Output: True
Explanation: 
The only way to decode it is two-bit character and one-bit character. So the last character is one-bit character.
Example 2:
Input: 
bits = [1, 1, 1, 0]
Output: False
Explanation: 
The only way to decode it is two-bit character and two-bit character. So the last character is NOT one-bit character.
Note:

1 <= len(bits) <= 1000.
bits[i] is always 0 or 1.

public class Solution {
    public bool IsOneBitCharacter(int[] bits) {
        return Helper(bits,0);
    }
    
    private bool Helper(int[] bits, int start){
        if(start == bits.Length-1){
            return bits[start]==0;
        }
        if(start > bits.Length-1){
            return false;
        }
        
        var valid1 = false;
        if(bits[start]==1){
            valid1 = Helper(bits,start+2);
        }
        
        var valid2 = false;
        if(bits[start]==0){
            valid2 = Helper(bits,start+1);
        }
        
        return valid1||valid2;
    }
}

 

 


Time Complexity: O(2^n) since it is a recursive call ( we can optimize it using Dynamic Programming)

Space Complexity: O(n) for stack trace