Run-Length Decoding- Google Top Interview Questions

Problem Statement :

Given a string s, consisting of digits and lowercase alphabet characters, that's a run-length encoded string, return its decoded version.

Note: The original string is guaranteed not to have numbers in it.


0 ≤ n ≤ 100,000 where n is the length of s

Example 1


s = "4a3b2c1d2a"



Solution :


                        Solution in C++ :

string solve(string s) {
    int l = 0, temp;
    string ans = "";
    for (char c : s) {
        temp = c - '0';
        if (temp >= 0 && temp <= 9)
            l = l * 10 + temp;
        else {
            while (l--) ans += c;
            l = 0;
    return ans;

                        Solution in Java :

import java.util.*;

class Solution {
    public String solve(String s) {
        StringBuilder sb = new StringBuilder();
        int v = 0;

        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (Character.isDigit(c)) {
                v = (v * 10) + Integer.parseInt("" + c);
            } else {
                for (int k = 0; k < v; k++) {
                v = 0;

        return sb.toString();

                        Solution in Python : 
class Solution:
    def solve(self, s):
        ans = ""
        c = ""
        for i in range(len(s)):
            if s[i].isalpha():
                ans = ans + int(c) * s[i]
                c = ""
                c = c + s[i]

        return ans

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