Decode Ways

class Solution {
public:
    int numDecodings(string s) {
        if (s.empty() || s[0] == '0') return 0;
        int prev2 = 1, prev1 = 1;
        for (int i = 1; i < (int)s.size(); ++i) {
            int curr = 0;
            if (s[i] != '0') curr += prev1;
            int two = (s[i - 1] - '0') * 10 + (s[i] - '0');
            if (two >= 10 && two <= 26) curr += prev2;
            prev2 = prev1;
            prev1 = curr;
        }
        return prev1;
    }
};

func numDecodings(s string) int {
    if len(s) == 0 || s[0] == '0' {
        return 0
    }
    prev2, prev1 := 1, 1
    for i := 1; i < len(s); i++ {
        curr := 0
        if s[i] != '0' {
            curr += prev1
        }
        two := int(s[i-1]-'0')*10 + int(s[i]-'0')
        if two >= 10 && two <= 26 {
            curr += prev2
        }
        prev2 = prev1
        prev1 = curr
    }
    return prev1
}

class Solution:
    def numDecodings(self, s: str) -> int:
        if not s or s[0] == '0':
            return 0
        prev2, prev1 = 1, 1
        for i in range(1, len(s)):
            curr = 0
            if s[i] != '0':
                curr += prev1
            two = int(s[i - 1]) * 10 + int(s[i])
            if 10 <= two <= 26:
                curr += prev2
            prev2, prev1 = prev1, curr
        return prev1

function numDecodings(s) {
    if (!s || s[0] === '0') return 0;
    let prev2 = 1, prev1 = 1;
    for (let i = 1; i < s.length; i++) {
        let curr = 0;
        if (s[i] !== '0') curr += prev1;
        const two = (s.charCodeAt(i - 1) - 48) * 10 + (s.charCodeAt(i) - 48);
        if (two >= 10 && two <= 26) curr += prev2;
        prev2 = prev1;
        prev1 = curr;
    }
    return prev1;
}

class Solution {
    public int numDecodings(String s) {
        if (s.isEmpty() || s.charAt(0) == '0') return 0;
        int prev2 = 1, prev1 = 1;
        for (int i = 1; i < s.length(); i++) {
            int curr = 0;
            if (s.charAt(i) != '0') curr += prev1;
            int two = (s.charAt(i - 1) - '0') * 10 + (s.charAt(i) - '0');
            if (two >= 10 && two <= 26) curr += prev2;
            prev2 = prev1;
            prev1 = curr;
        }
        return prev1;
    }
}

function numDecodings(s: string): number {
    if (!s || s[0] === '0') return 0;
    let prev2 = 1, prev1 = 1;
    for (let i = 1; i < s.length; i++) {
        let curr = 0;
        if (s[i] !== '0') curr += prev1;
        const two = (s.charCodeAt(i - 1) - 48) * 10 + (s.charCodeAt(i) - 48);
        if (two >= 10 && two <= 26) curr += prev2;
        prev2 = prev1;
        prev1 = curr;
    }
    return prev1;
}