Create countPalindromicSubstrings.cpp

Author: SteffiKeranJ

Dynamic-Programming/countPalindromicSubstrings.cpp

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+/** 
+647. Palindromic Substrings
+Given a string s, return the number of palindromic substrings in it.
+
+A string is a palindrome when it reads the same backward as forward.
+
+A substring is a contiguous sequence of characters within the string.
+
+ 
+
+Example 1:
+
+Input: s = "abc"
+Output: 3
+Explanation: Three palindromic strings: "a", "b", "c".
+Example 2:
+
+Input: s = "aaa"
+Output: 6
+Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".
+ 
+
+Constraints:
+
+1 <= s.length <= 1000
+s consists of lowercase English letters.
+**/
+
+class Solution {
+public:
+    int countSubstrings(string s) {
+        int count = 0;
+        int n = s.size();
+        if(n == 1) return 1;
+        bool dp[1001][1001] = {false};
+        for(int i=0; i <n;++i ) {
+            dp[i][i] = true;
+            count++;
+        }
+        for(int i = n-1; i >=0; --i) {
+            for(int j = i+1; j <n;++j) {
+                if(s[i] == s[j]) {
+                    if(j-i==1 || dp[i+1][j-1] == true) {
+                        dp[i][j] = true;
+                        count++;
+                    }
+                }
+            }
+        }
+        return count;
+    }
+};