647. Palindromic Substrings

Aug 14

Author: TonyKim9401

palindromic-substrings/TonyKim9401.java

@@ -0,0 +1,52 @@
+class Solution {
+    public int countSubstrings(String s) {
+        /**
+         * time complexity: O(n);
+         * space complexity: O(1);
+         */
+
+        int output = 0;
+        // ex) abc
+        // 1. abc
+        // 2. bc
+        // 3. c
+        for (int i = 0; i < s.length(); i++) {
+            output += palindromicCheck(s.substring(i, s.length()));
+        }
+        return output;
+    }
+
+    public int palindromicCheck(String str) {
+        int result = 0;
+        /**
+         * ex) abc
+         * 1. a
+         * 2. ab
+         * 3. abc
+         */
+        for (int i = 0; i < str.length(); i++) {
+            String candidate = str.substring(0, i+1);
+            if (palindromic(candidate)) {
+                result += 1;
+            }
+        }
+        return result;
+    }
+
+    public boolean palindromic(String candidate) {
+        int start = 0;
+        int end = candidate.length() - 1;
+
+        /** ex)abc
+         * 1. a -> true
+         * 2. ab -> false
+         * 3. abc -> false
+         */
+        while (start < end) {
+            if (candidate.charAt(start) != candidate.charAt(end)) return false;
+            start += 1;
+            end -= 1;
+        }
+        return true;
+    }
+}