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+# [231. Power of Two](https://leetcode.com/problems/power-of-two/description/)
+# 思路
+求n是否是2的幂。   
+1. 首先若n不是正数肯定直接返回false，若n为1直接返回true；   
+2. 若n是不为1的奇数返回false；
+3. 令n = n / 2，若n=1则返回true否则返回第2步。   
+# C++
+```
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        if(n <= 0) return false;
+        if(n == 1) return true;
+        while(n > 1){
+            if(n % 2 == 1) return false;
+            n /= 2;
+        }
+        return true;
+    }
+};
+```