feat: add solutions to lc problem: No.0564

Author: AE-Hertz

solution/0500-0599/0564.Find the Closest Palindrome/Solution.js

@@ -0,0 +1,45 @@
+/**
+ * @param {string} n
+ * @return {string}
+ */
+
+function nearestPalindromic(n) {
+    const x = BigInt(n);
+    let ans = null;
+
+    for (const t of getCandidates(n)) {
+        if (
+            ans === null ||
+            absDiff(t, x) < absDiff(ans, x) ||
+            (absDiff(t, x) === absDiff(ans, x) && t < ans)
+        ) {
+            ans = t;
+        }
+    }
+
+    return ans.toString();
+}
+
+function getCandidates(n) {
+    const length = n.length;
+    const res = new Set();
+
+    res.add(BigInt(Math.pow(10, length - 1) - 1));
+    res.add(BigInt(Math.pow(10, length) + 1)); 
+
+    const left = BigInt(n.substring(0, Math.ceil(length / 2)));
+
+    for (let i = left - 1n; i <= left + 1n; i++) {
+        const prefix = i.toString();
+        const t = prefix + prefix.split('').reverse().slice(length % 2).join('');
+        res.add(BigInt(t));
+    }
+
+    res.delete(BigInt(n));
+    return res;
+}
+
+function absDiff(a, b) {
+    return a > b ? a - b : b - a;
+}
+