feat(cpp): add swap_odd_and_even_bits.cpp

Author: ongshunping

cpp/Bit Manipulation/swap_odd_and_even_bits.cpp

@@ -0,0 +1,9 @@
+unsigned int swapOddAndEvenBits(unsigned int n) {
+    unsigned int evenMask = 0x55555555; // 01010101010101010101010101010101
+    unsigned int oddMask  = 0xAAAAAAAA; // 10101010101010101010101010101010
+    unsigned int evenBits = n & evenMask;
+    unsigned int oddBits  = n & oddMask;
+    // Shift the even bits to the left, the odd bits to the right, and
+    // merge these shifted values together.
+    return (evenBits << 1) | (oddBits >> 1);
+}