Create Longest Palindromic Substring.cpp

Longest Palindromic Substring.cpp

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+#include<bits/stdc++.h>
+#include <string>
+using namespace std;
+string solve(string s)
+{
+    int n=s.length();
+    bool dp[n][n]={false};
+    // single character is a palindrome of length one.
+    for(int i=0; i<n; i++)
+    dp[i][i]=true;
+    // check of palindrome of size two exists
+    for(int i=0; i<n-1; i++)
+    if(s[i]==s[i+1])
+    dp[i][i+1]=true;
+    int st,mx=-1;
+    //for palindrome of size = 3  we make two loops
+    for(int len=2 ; len<n; len++) // len is representing index
+    {
+        for(int i=0; i<n-len; i++)
+        {
+            // you may replace (i+len) with another variable like ' j '
+            if(s[i+len]==s[i] && dp[i+1][i+len-1]) {
+                        dp[i][i+len]=true;
+                        if(mx < len+1) // since len is the index ( doing for substr() )
+                        {              // so, mx = len+1 
+                            mx=len+1;
+                            st=i;
+                        }
+                    }
+        }
+    }
+
+    return s.substr(st,mx);
+
+}
+int main()
+{
+    string s= "abadfgdcbc";
+    cout<<solve(s);
+}