swap bit range done

Author: Ram swaroop

src/me/ramswaroop/bits/SwapBits.java

@@ -0,0 +1,45 @@
+package me.ramswaroop.bits;
+
+/**
+ * Created by IntelliJ IDEA.
+ *
+ * @author: ramswaroop
+ * @date: 6/13/15
+ * @time: 4:45 PM
+ */
+public class SwapBits {
+
+    /**
+     * Swaps {@param length} bits in {@param n} starting from
+     * {@param pos1} with bits starting from {@param pos2}.
+     * <p/>
+     * For example,
+     * x = 28 (11100)
+     * p1 = 0 (Start from first bit from right side)
+     * p2 = 3 (Start from 4th bit from right side)
+     * l = 2 (No of bits to be swapped)
+     * Output:
+     * 7 (00111)
+     *
+     * @param n
+     * @param pos1   starts from 0
+     * @param pos2   starts from 0
+     * @param length
+     * @return
+     */
+    public static int swapBitRangeInNumber(int n, int pos1, int pos2, int length) {
+        int set1 = (n >> pos1) & ((1 << length) - 1); // 1st set of bits to be swapped
+        int set2 = (n >> pos2) & ((1 << length) - 1); // 2nd set of bits to be swapped
+        int xor = set1 ^ set2; // difference pattern between the bits to be swapped
+
+        return n ^ (xor << pos1) ^ (xor << pos2);   // XORing the difference pattern at the appropriate
+        // position of the bits to be swapped gives us the result
+        // (this logic is similar to swapping bits using XOR)
+    }
+
+    public static void main(String a[]) {
+        System.out.println(swapBitRangeInNumber(47, 1, 5, 3));
+        System.out.println(swapBitRangeInNumber(28, 0, 3, 2));
+        System.out.println(swapBitRangeInNumber(269, 1, 3, 2));
+    }
+}