Decode Ways LeetCode Solution – Queslers

Problem – Decode Ways

A message containing letters from A-Z can be encoded into numbers using the following mapping:

'A' -> "1"
'B' -> "2"
...
'Z' -> "26"

To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways). For example, "11106" can be mapped into:

  • "AAJF" with the grouping (1 1 10 6)
  • "KJF" with the grouping (11 10 6)

Note that the grouping (1 11 06) is invalid because "06" cannot be mapped into 'F' since "6" is different from "06".

Given a string s containing only digits, return the number of ways to decode it.

The test cases are generated so that the answer fits in a 32-bit integer.

Example 1:

Input: s = "12"
Output: 2
Explanation: "12" could be decoded as "AB" (1 2) or "L" (12).

Example 2:

Input: s = "226"
Output: 3
Explanation: "226" could be decoded as "BZ" (2 26), "VF" (22 6), or "BBF" (2 2 6).

Example 3:

Input: s = "06"
Output: 0
Explanation: "06" cannot be mapped to "F" because of the leading zero ("6" is different from "06").

Constraints:

  • 1 <= s.length <= 100
  • s contains only digits and may contain leading zero(s).

Decode Ways LeetCode Solution in C++

    int numDecodings(string s) {
        return s.empty() ? 0: numDecodings(0,s);    
    }
    int numDecodings(int p, string& s) {
        int n = s.size();
        if(p == n) return 1;
        if(s[p] == '0') return 0; // sub string starting with 0 is not a valid encoding
        int res = numDecodings(p+1,s);
        if( p < n-1 && (s[p]=='1'|| (s[p]=='2'&& s[p+1]<'7'))) res += numDecodings(p+2,s);
        return res;
    }

Decode Ways LeetCode Solution in Java

	public int numDecodings(String s) {
        return s.length()==0?0:numDecodings(0,s);      
    }
    private int numDecodings(int p, String s) {
        int n=s.length();
        if(p==n) return 1;
        if(s.charAt(p)=='0') return 0;
        int res=numDecodings(p+1,s);
        if(p<n-1&&(s.charAt(p)=='1'||s.charAt(p)=='2'&&s.charAt(p+1)<'7')) 
			res+=numDecodings(p+2,s);
        return res;
    }

Decode Ways LeetCode Solution in Python

def numDecodings(s): 
	if not s:
		return 0

	dp = [0 for x in range(len(s) + 1)] 
	
	# base case initialization
	dp[0] = 1 
	dp[1] = 0 if s[0] == "0" else 1   #(1)

	for i in range(2, len(s) + 1): 
		# One step jump
		if 0 < int(s[i-1:i]) <= 9:    #(2)
			dp[i] += dp[i - 1]
		# Two step jump
		if 10 <= int(s[i-2:i]) <= 26: #(3)
			dp[i] += dp[i - 2]
	return dp[len(s)]
Decode Ways LeetCode Solution Review:

In our experience, we suggest you solve this Decode Ways LeetCode Solution and gain some new skills from Professionals completely free and we assure you will be worth it.

If you are stuck anywhere between any coding problem, just visit Queslers to get the Decode Ways LeetCode Solution

Find on LeetCode

Conclusion:

I hope this Decode Ways LeetCode Solution would be useful for you to learn something new from this problem. If it helped you then don’t forget to bookmark our site for more Coding Solutions.

This Problem is intended for audiences of all experiences who are interested in learning about Data Science in a business context; there are no prerequisites.

Keep Learning!

More Coding Solutions >>

LeetCode Solutions

Hacker Rank Solutions

CodeChef Solutions

Leave a Reply

Your email address will not be published.