**Run-Length Encoding - Amazon Top Interview Questions**

### Problem Statement :

Given a string s, return its run-length encoding. You can assume the string to be encoded have no digits and consists solely of alphabetic characters. Constraints n ≤ 100,000 where n is the length of s Example 1 Input s = "aaaabbbccdaa" Output "4a3b2c1d2a" Example 2 Input s = "abcde" Output "1a1b1c1d1e" Example 3 Input s = "aabba" Output "2a2b1a" Example 4 Input s = "aaaaaaaaaa" Output "10a"

### Solution :

` ````
Solution in C++ :
string solve(string s) {
string answer;
int n = s.size();
int j = 0;
int count = 0;
for (int i = 0; i < n;) {
char character = s[i];
while (j < n && s[j] == character) {
j++;
}
answer.append(to_string(j - i));
answer.append(1, character);
i = j;
}
return answer;
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public String solve(String s) {
if (s.length() == 0)
return s;
StringBuilder result = new StringBuilder();
char preChar = s.charAt(0);
int count = 0;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == preChar)
count++;
else {
result.append(count).append(preChar);
preChar = s.charAt(i);
count = 1;
}
}
result.append(count).append(preChar);
return result.toString();
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, s):
return "".join([str(len(list(j))) + str(i) for i, j in groupby(s)])
```

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