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+# [476. Number Complement](https://leetcode.com/problems/number-complement/description/)
+# 思路
+先将num的bit全部翻转，再看num有多少前导0，然后用一个合适的mask对之前的翻转结果进行与操作即可。
+# C++
+``` C++
+class Solution {
+public:
+    int findComplement(int num) {
+        if(num == 0) return 1;
+        int i, res = ~num, mask=0xffffffff;
+        while(mask & num) mask <<= 1;
+        return res & ~mask;
+    }
+};
+```