[28 May, 2020] Add cpp solution2 and solution3

Author: kerms

May-LeetCoding-Challenge/28-Counting-Bits/Counting-Bits.cpp

@@ -12,4 +12,47 @@ class Solution {
         }
         return ans;
     }
-};
+};
+
+class Solution2 {
+public:
+    inline int numberOfSetBits(int i)
+    {
+        i = i - ((i >> 1) & 0x55555555);
+        i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
+        return (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
+    }
+    
+    vector<int> countBits(int num) {
+        vector<int> v;  
+        for (int i = 0; i <= num ; ++i)
+            v.push_back(numberOfSetBits(i));
+        return v;
+    }
+};
+
+class Solution3 {
+public:
+    vector<int> countBits(int num) {
+        vector<int> v(num+1);
+        int n = 1, src = 0;
+        
+        /* init */
+        v[0] = 0;
+        
+        while ((n<<1)+n <= num) {
+            for (;src<n;++src) v[src+n] = v[src]+1;
+            n += n;
+            memcpy(&v[n], &v[src], (n-src)*sizeof(int));
+        }
+        
+        if (num < n*2) {
+            for (;src<=num-n;++src) v[src+n] = v[src]+1;
+            return v;
+        }
+        for (;src<n;++src) v[src+n] = v[src]+1;
+        n += n;
+        memcpy(&v[n], &v[src], (num-n+1)*sizeof(int));
+        return v;
+    }
+};