**Smallest Number With No Adjacent Duplicates - Google Top Interview Questions**

### Problem Statement :

You are given a string s containing "1", "2", "3" and "?". Given that you can replace any “?” with "1", "2" or "3", return the smallest number you can make as a string such that no two adjacent digits are the same. Constraints n ≤ 100,000 where n is the length of s Example 1 Input s = "3?2??" Output "31212" Example 2 Input s = "???" Output "121"

### Solution :

` ````
Solution in C++ :
string solve(string s) {
for (int i = 0; i < s.size(); i++) {
if (s[i] == '?') {
bool one = true, two = true;
if (i > 0) {
if (s[i - 1] - '0' == 1) one = false;
if (s[i - 1] - '0' == 2) two = false;
}
if (i < s.size() - 1) {
if (s[i + 1] - '0' == 1) one = false;
if (s[i + 1] - '0' == 2) two = false;
}
if (one) {
s[i] = '1';
} else if (two)
s[i] = '2';
else
s[i] = '3';
}
}
return s;
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public String solve(String s) {
char[] c = s.toCharArray();
int N = s.length();
for (int i = 0; i < N; i++) {
if (c[i] != '?')
continue;
boolean[] b = new boolean[3];
if (i > 0)
b[c[i - 1] - '1'] = true;
if (i < N - 1 && c[i + 1] != '?')
b[c[i + 1] - '1'] = true;
for (int j = 0; j < 3; j++) {
if (!b[j]) {
c[i] = (char) (j + '1');
break;
}
}
}
return new String(c);
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, s):
A = list(s)
for i, c in enumerate(A):
if c == "?":
for d in "123":
A[i] = d
if i - 1 >= 0 and A[i] == A[i - 1]:
continue
if i + 1 < len(A) and A[i] == A[i + 1]:
continue
break
return "".join(A)
```

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