remove_duplicate_letters

Author: hitzzc

README.md

@@ -229,6 +229,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [312. Burst Balloons](https://github.com/hitzzc/go-leetcode/tree/master/burst_balloons)
 #### [313. Super Ugly Number](https://github.com/hitzzc/go-leetcode/tree/master/super_ugly_number)
 #### [315. Count of Smaller Numbers After Self](https://github.com/hitzzc/go-leetcode/tree/master/count_of_smaller_numbers_after_self)
+#### [316. Remove Duplicate Letters](https://github.com/hitzzc/go-leetcode/tree/master/remove_duplicate_letters)
 
 
 

remove_duplicate_letters/remove_duplicate_letters.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    string removeDuplicateLetters(string s) {
+    	if (s.size() == 0) return "";
+        unordered_map<char, int> count;
+        for (int i = 0; i < s.size(); ++i) {
+        	++count[s[i]];
+        }
+        unordered_set<char> existed = {s[0]};
+        vector<char> vec = {s[0]};
+        --count[s[0]];
+        for (int i = 1; i < s.size(); ++i) {
+       		--count[s[i]];
+        	if (existed.count(s[i]) == 0) {
+        		while (!vec.empty()) {
+        			char back = vec.back();
+        			if (back <= s[i] || count[back] == 0) break;
+        			vec.pop_back();
+        			existed.erase(back);
+        		}
+	        	vec.push_back(s[i]);
+				existed.insert(s[i]);
+        	}
+        }
+        string ret;
+        for (auto ch: vec) {
+        	ret += ch;
+        }
+        return ret;
+    }
+};