largest panlindrome product

Author: chen0040

.idea/workspace.xml

@@ -403,6 +403,7 @@ codes may not be optimized
 1. [Path Sum III](https://leetcode.com/problems/path-sum-iii/description/)
 1. [Minimum Moves to Equal Array Elements](https://leetcode.com/problems/minimum-moves-to-equal-array-elements/description/)
 1. [Repeated Substring Patterns](https://leetcode.com/problems/repeated-substring-pattern/description/)
+1. [Largest Panlindrome Product](https://leetcode.com/problems/largest-palindrome-product/description/)
 
 ### Day 19 - Medium
 

README.md

@@ -0,0 +1,47 @@
+package com.github.chen0040.leetcode.day19.easy;
+
+
+/**
+ * Created by xschen on 14/8/2017.
+ *
+ * link: https://leetcode.com/problems/largest-palindrome-product/description/
+ */
+public class LargestPanlinedromeProduct {
+   public class Solution {
+      public int largestPalindrome(int n) {
+
+         if(n == 1) return 9;
+
+         int upperBound = (int)Math.pow(10, n) - 1;
+         int lowerBound = (int)Math.pow(10, n-1);
+
+         long maxNumber = (long)upperBound * (long)upperBound;
+
+         int firstHalf = (int)(maxNumber / (long)Math.pow(10, n));
+         while(true) {
+            long candidate = createPanlindrome(firstHalf);
+            for(long i = upperBound; i >= lowerBound; --i) {
+               if (i * i < candidate) {
+                  break;
+               }
+
+               if(candidate % i == 0) {
+                  return (int)(candidate % 1337);
+               }
+            }
+            firstHalf--;
+            if(firstHalf < 0) break;
+         }
+         return -1;
+      }
+
+      long createPanlindrome(int firstHalf) {
+         StringBuilder sb = new StringBuilder();
+         sb.append(firstHalf);
+         sb.reverse();
+         String str = firstHalf + sb.toString();
+         return Long.parseLong(str);
+
+      }
+   }
+}