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Author: assassint2017

Bitwise AND of Numbers Range/Bitwise_AND_of_Numbers_Range.cpp

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+// 典型的位运算的题目 解题思路很巧妙
+// 思路一，比较低效
+
+// Runtime: 8 ms, faster than 95.68% of C++ online submissions for Bitwise AND of Numbers Range.
+// Memory Usage: 8.6 MB, less than 5.45% of C++ online submissions for Bitwise AND of Numbers Range.
+
+class Solution 
+{
+public:
+    int rangeBitwiseAnd(int m, int n) 
+    {
+        vector<bool> memo(31, false);
+
+        for (int i = 0; i < 31; i++)
+        {
+            if (m == n && m & 1 == 1)
+                memo[i] = true;
+
+            m >>= 1;
+            n >>= 1;
+
+            if (m == 0 && n == 0)
+                break;
+        }
+
+        // 计算最终的结果
+        int res = 0;
+        for (int i = 30; i >= 0; i--)
+        {
+            res <<= 1;
+            if (memo[i])
+                res++;
+        }
+
+        return res;
+    }
+};
+
+// 思路二 相对高效
+
+// Runtime: 8 ms, faster than 95.68% of C++ online submissions for Bitwise AND of Numbers Range.
+// Memory Usage: 8 MB, less than 89.81% of C++ online submissions for Bitwise AND of Numbers Range.
+
+class Solution 
+{
+public:
+    int rangeBitwiseAnd(int m, int n) 
+    {
+        if (m == 0 || n == 0)
+            return 0;
+
+        int factor = 0;
+        while (m != n)    
+        {
+            m >>= 1;
+            n >>= 1;
+            factor++;
+        }
+
+        return m << factor;
+    }
+};

Bitwise AND of Numbers Range/Bitwise_AND_of_Numbers_Range.py

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+# 思路一的py代码
+
+class Solution:
+    def rangeBitwiseAnd(self, m: int, n: int) -> int:
+        memo = [False] * 31
+
+        for i in range(31):
+            if m == n and m & 1 is 1:
+                memo[i] = True
+            m >>= 1
+            n >>= 1
+
+            if m is 0 and n is 0:
+                break
+        
+        res = 0
+        for i in range(30, -1, -1):
+            res <<= 1
+            if memo[i]:
+                res += 1
+        
+        return res
+    
+# 思路二的py代码
+
+# Runtime: 60 ms, faster than 86.48% of Python3 online submissions for Bitwise AND of Numbers Range.
+# Memory Usage: 13.4 MB, less than 21.68% of Python3 online submissions for Bitwise AND of Numbers Range.
+
+class Solution:
+    def rangeBitwiseAnd(self, m: int, n: int) -> int:
+        
+        if m is 0 and n is 0:
+            return 0
+        
+        factor = 0
+        while m != n:
+            m >>= 1
+            n >>= 1
+            factor += 1
+        
+        return m << factor