3 problems

Author: hitzzc

README.md

@@ -230,7 +230,10 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [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)
-#### [318. Maximum Product of Word Lengths  ](https://github.com/hitzzc/go-leetcode/tree/master/maximum_product_of_word_lengths)
+#### [318. Maximum Product of Word Lengths ](https://github.com/hitzzc/go-leetcode/tree/master/maximum_product_of_word_lengths)
+#### [319. Bulb Switcher](https://github.com/hitzzc/go-leetcode/tree/master/bulb_switcher)
+#### [322. Coin Change](https://github.com/hitzzc/go-leetcode/tree/master/coin_change)
+#### [326. Power of Three](https://github.com/hitzzc/go-leetcode/tree/master/power_of_three)
 
 
 

bulb_switcher/bulb_switcher.cpp

@@ -0,0 +1,10 @@
+class Solution {
+public:
+    int bulbSwitch(int n) {
+        int ret = 0;
+        for (int i = 1; i*i <= n; ++i) {
+        	++ret;
+        }
+        return ret;
+    }
+};

coin_change/coin_change.cpp

@@ -0,0 +1,13 @@
+class Solution {
+public:
+    int coinChange(vector<int>& coins, int amount) {
+        vector<int> dp(amount+1, amount+1);
+        dp[0] = 0;
+        for (int i = 1; i < dp.size(); ++i) {
+        	for (auto coin: coins) {
+        		if (i >= coin) dp[i] = min(dp[i], dp[i-coin]+1);
+        	}
+        }
+        return dp.back() == amount+1 ? -1: dp.back();
+    }
+};

power_of_three/power_of_three.cpp

@@ -0,0 +1,6 @@
+class Solution {
+public:
+    bool isPowerOfThree(int n) {
+        return (n > 0 && 1162261467 % n == 0);
+    }
+};