> For the complete documentation index, see [llms.txt](https://coding-9.gitbook.io/untitled/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://coding-9.gitbook.io/untitled/string/medium/5.-longest-palindromic-substring.md).
# 5. Longest Palindromic Substring
## Problem Statement
Given a string `s`, return *the longest*
*palindromic* *substring* in `s`.
**Example 1:**
Input: s = "babad"
Output: "bab"
Explanation: "aba" is also a valid answer.
**Example 2:**
Input: s = "cbbd"
Output: "bb"
**Constraints:**
* `1 <= s.length <= 1000`
* `s` consist of only digits and English letters.
## Intuition
```
Rather coming from edges
Expand from the centre
This will eliminate the extra loop
N^2
```
### Links
### Video Links
### Approach 1:
```
Scanning from centre
```
{% code title="C++" lineNumbers="true" %}
```cpp
class Solution {
public:
string ans = "";
void expand(string &s , int left ,int right){
while(left >= 0 && right < s.size()){
if(s[left] != s[right])
break;
left--,right++;
}
if(ans.size() < right - left )
ans = s.substr(left + 1 , right - left - 1);
}
string longestPalindrome(string s) {
for(int i = 0 ; i < s.size() ; i++){
expand(s , i , i);
expand(s , i , i+1);
}
return ans;
}
};
```
{% endcode %}
### Approach 2:
```
```
{% code title="C++" lineNumbers="true" %}
```cpp
```
{% endcode %}
### Approach 3:
```
```
{% code title="C++" lineNumbers="true" %}
```cpp
```
{% endcode %}
### Approach 4:
```
```
{% code title="C++" lineNumbers="true" %}
```cpp
```
{% endcode %}
### Similar Problems
###
---
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