palindrome_pairs

Author: hitzzc

README.md

@@ -240,6 +240,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [332. Reconstruct Itinerary](https://github.com/hitzzc/go-leetcode/tree/master/reconstruct_ltinerary)
 #### [334. Increasing Triplet Subsequence](https://github.com/hitzzc/go-leetcode/tree/master/increasing_triplet_subsequence)
 #### [335. Self Crossing](https://github.com/hitzzc/go-leetcode/tree/master/self_crossing)
+#### [336. Palindrome Pairs](https://github.com/hitzzc/go-leetcode/tree/master/palindrome_pairs)
 
 
 

palindrome_pairs/palindrome_pairs.cpp

@@ -0,0 +1,37 @@
+class Solution {
+public:
+    vector<vector<int>> palindromePairs(vector<string>& words) {
+        vector<vector<int>> results;
+        unordered_map<string, int> mapping;
+        set<int> index_set;
+        for (int i = 0; i < words.size(); ++i) {
+        	mapping[words[i]] = i;
+        	index_set.insert(words[i].size());
+        }
+        for (int i = 0; i < words.size(); ++i) {
+        	string word = words[i];
+        	int len = word.size();
+        	reverse(word.begin(), word.end());
+        	if (mapping.count(word) != 0 && mapping[word] != i) {
+        		results.push_back(vector<int>{i, mapping[word]});
+        	}
+        	for (auto j = index_set.begin(); j != index_set.find(word.size()); ++j) {
+        		int d = *j;
+        		if (is_palindrome(word, 0, len - d - 1) && mapping.count(word.substr(len - d))) {
+                    results.push_back({i, mapping[word.substr(len - d)]});
+                }
+                if (is_palindrome(word, d, len - 1) && mapping.count(word.substr(0, d))) {
+                    results.push_back({mapping[word.substr(0, d)], i});
+                }
+        	}
+        }
+        return results;
+    }
+
+    bool is_palindrome(string& s, int i, int j) {
+    	while (i < j) {
+    		if (s[i++] != s[j--]) return false;
+    	}
+    	return true;
+    }
+};