solution: palindromic substrings

Author: Jeongwon Na

palindromic-substrings/njngwn.java

@@ -0,0 +1,36 @@
+// Time Complexity: O(n*n), n: s.length()
+// Space Complexity: O(1)
+class Solution {
+    public int countSubstrings(String s) {
+        int cnt = 0;
+
+        for (int i = 0; i < s.length(); i++, cnt++) {   // i: center of palindrom
+            // odd number palindrom: e.g. aba
+            int left = i-1, right = i+1;
+
+            while (left >= 0 && right < s.length()) {
+                if (s.charAt(left) != s.charAt(right)) {
+                    break;
+                }
+                cnt++;
+                left--;
+                right++;
+            }
+
+            // even number palindrom: e.g. abba
+            left = i;
+            right = i+1;
+
+            while (left >= 0 && right < s.length()) {
+                if (s.charAt(left) != s.charAt(right)) {
+                    break;
+                }
+                cnt++;
+                left--;
+                right++;
+            }
+        }
+
+        return cnt;
+    }
+}