Multiply Strings

class Solution {
public:
    string multiply(string a, string b) {
        if (a == "0" || b == "0") return "0";
        int m = a.size(), n = b.size();
        vector<int> r(m + n, 0);
        for (int i = m - 1; i >= 0; --i)
            for (int j = n - 1; j >= 0; --j) {
                int p = (a[i] - '0') * (b[j] - '0');
                int sum = p + r[i + j + 1];
                r[i + j + 1] = sum % 10;
                r[i + j] += sum / 10;
            }
        string out;
        for (int d : r) {
            if (!out.empty() || d != 0) out.push_back('0' + d);
        }
        return out;
    }
};

func multiply(a string, b string) string {
    if a == "0" || b == "0" {
        return "0"
    }
    m, n := len(a), len(b)
    r := make([]int, m+n)
    for i := m - 1; i >= 0; i-- {
        for j := n - 1; j >= 0; j-- {
            p := int(a[i]-'0') * int(b[j]-'0')
            sum := p + r[i+j+1]
            r[i+j+1] = sum % 10
            r[i+j] += sum / 10
        }
    }
    out := []byte{}
    for _, d := range r {
        if len(out) > 0 || d != 0 {
            out = append(out, byte('0'+d))
        }
    }
    return string(out)
}

class Solution:
    def multiply(self, a: str, b: str) -> str:
        if a == "0" or b == "0":
            return "0"
        m, n = len(a), len(b)
        r = [0] * (m + n)
        for i in range(m - 1, -1, -1):
            for j in range(n - 1, -1, -1):
                p = (ord(a[i]) - ord('0')) * (ord(b[j]) - ord('0'))
                total = p + r[i + j + 1]
                r[i + j + 1] = total % 10
                r[i + j] += total // 10
        out = []
        for d in r:
            if out or d != 0:
                out.append(chr(ord('0') + d))
        return "".join(out)

function multiply(a, b) {
    if (a === "0" || b === "0") return "0";
    const m = a.length, n = b.length;
    const r = new Array(m + n).fill(0);
    for (let i = m - 1; i >= 0; i--) {
        for (let j = n - 1; j >= 0; j--) {
            const p = (a.charCodeAt(i) - 48) * (b.charCodeAt(j) - 48);
            const sum = p + r[i + j + 1];
            r[i + j + 1] = sum % 10;
            r[i + j] += Math.floor(sum / 10);
        }
    }
    let out = "";
    for (const d of r) {
        if (out.length > 0 || d !== 0) out += d;
    }
    return out;
}

class Solution {
    public String multiply(String a, String b) {
        if (a.equals("0") || b.equals("0")) return "0";
        int m = a.length(), n = b.length();
        int[] r = new int[m + n];
        for (int i = m - 1; i >= 0; i--) {
            for (int j = n - 1; j >= 0; j--) {
                int p = (a.charAt(i) - '0') * (b.charAt(j) - '0');
                int sum = p + r[i + j + 1];
                r[i + j + 1] = sum % 10;
                r[i + j] += sum / 10;
            }
        }
        StringBuilder out = new StringBuilder();
        for (int d : r) {
            if (out.length() > 0 || d != 0) out.append((char) ('0' + d));
        }
        return out.toString();
    }
}

function multiply(a: string, b: string): string {
    if (a === "0" || b === "0") return "0";
    const m = a.length, n = b.length;
    const r: number[] = new Array(m + n).fill(0);
    for (let i = m - 1; i >= 0; i--) {
        for (let j = n - 1; j >= 0; j--) {
            const p = (a.charCodeAt(i) - 48) * (b.charCodeAt(j) - 48);
            const sum = p + r[i + j + 1];
            r[i + j + 1] = sum % 10;
            r[i + j] += Math.floor(sum / 10);
        }
    }
    let out = "";
    for (const d of r) {
        if (out.length > 0 || d !== 0) out += d;
    }
    return out;
}