add Palindromic Substrings solution

Author: HoonDongKang

palindromic-substrings/HoonDongKang.ts

@@ -0,0 +1,57 @@
+/**
+ * [Problem]: [647] Palindromic Substrings
+ * (https://leetcode.com/problems/palindromic-substrings/description/)
+ */
+
+function countSubstrings(s: string): number {
+    //시간복잡도 O(n^3)
+    //공간복잡도 O(1)
+    function bruteForceFunc(s: string): number {
+        let count = 0;
+
+        for (let i = 0; i < s.length; i++) {
+            for (let j = i; j < s.length; j++) {
+                if (isPanlindrome(i, j)) count++;
+            }
+        }
+
+        function isPanlindrome(left: number, right: number): boolean {
+            while (left < right) {
+                if (s[left] !== s[right]) return false;
+                left++;
+                right--;
+            }
+
+            return true;
+        }
+
+        return count;
+    }
+    //시간복잡도 O(n^2)
+    //공간복잡도 O(n^2)
+    function dpFunc(s: string): number {
+        const dp = new Map<string, boolean>();
+        let count = 0;
+
+        for (let end = 0; end < s.length; end++) {
+            for (let start = end; start >= 0; start--) {
+                const key = `${start},${end}`;
+                if (start === end) {
+                    dp.set(key, true);
+                } else if (start + 1 === end) {
+                    dp.set(key, s[start] === s[end]);
+                } else {
+                    const innerKey = `${start + 1},${end - 1}`;
+                    const isInnerPalindrome = dp.get(innerKey) || false;
+                    dp.set(key, s[start] === s[end] && isInnerPalindrome);
+                }
+
+                if (dp.get(key)) {
+                    count++;
+                }
+            }
+        }
+
+        return count;
+    }
+}