Day-36: BFS- Graph and bit manipulation prob

Author: mandliya

README.md

@@ -4,9 +4,9 @@
 
 | Current Status|     Stats     |
 | :------------: | :----------: |
-| Total Problems | 54 |
-| Current Streak | 35 |
-| Longest Streak | 35 ( August 17, 2015 - September 20, 2015 ) |
+| Total Problems | 56 |
+| Current Streak | 36 |
+| Longest Streak | 36 ( August 17, 2015 - September 21, 2015 ) |
 
 </center>
 
@@ -60,6 +60,7 @@ Include contains single header implementation of data structures and some algori
 |Given a vector of numbers, only one number occurs odd number of times, find the number.| [find_odd_one_out.cpp](bit_manipulation/find_odd_one_out.cpp)|
 | Given two integers, determine if their sum would be interger overflow.| [integerOverflow.cpp](bit_manipulation/integerOverflow.cpp)|
 | How many bit flip operation would require to convert number A to B. | [countNumberOfBitFlips.cpp](bit_manipulation/countNumberOfBitFlips.cpp)|
+| Given a number x and two positions (from right side) in binary representation of x, write a function that swaps n right bits at given two positions and returns the result. It is also given that the two sets of bits do not overlap.|[swapSetOfBits.cpp](bit_manipulation/swapSetOfBits.cpp)|
 
 ### Cracking the coding interview problems
 | Problem | Solution |
@@ -109,3 +110,4 @@ Include contains single header implementation of data structures and some algori
 | Problem | Solution |
 | :------------ | :----------: |
 | Depth First Traversal of a Graph | [dfsDemo.cpp](graph_problems/dfsDemo.cpp) |
+| Breadth First Traversal of a Graph | [bfsDemo.cpp](graph_problems/bfsDemo.cpp) |

bit_manipulation/swapSetOfBits.cpp

@@ -0,0 +1,46 @@
+/**
+ * Problem - Given a number 'num' and two positions (p1 and p2 from right side) in binary representation of num,
+ *  write a function that swaps n bits at given two positions and returns the result.
+ *  It is also given that the two sets of bits do not overlap.
+ */
+
+#include <iostream>
+
+int swapBits(unsigned int num, unsigned int p1,
+             unsigned int p2, unsigned int n )
+{
+  //Step1 lets form a number set1 by  moving  n bits at position p1 to the rightmost
+  unsigned int set1 = (num >> p1 ) & ((1U << n) - 1);
+  // Lets understand what we just did.
+  // Part1 : (num >> p1), we just right shifted num so that bit at p1 position takes 0th postion.
+  // Part2 : Remember we needed n bits from position p1(which has become position 0)
+  //         So, (1U << n) moves 1 to nth bit, i.e. it the value formed by this movement is 2^n
+  //         Now, If we substract 1 from the (2^n), it will give us all 1's for n positions.
+  //         For example (1U << 3) = 1000
+  //         and (1U << 3) - 1 = 0111
+  // Part3 : Thus Part1 & Part2 will give as n bits which were at P1 (now moved to 0)
+
+  //similarly for p2
+  unsigned int set2 = (num >> p2) & ((1U << n) - 1);
+
+  // xor two sets ( we are doing similar to xor swap algorithm )
+  // https://en.wikipedia.org/wiki/XOR_swap_algorithm
+  unsigned int xorSets = set1 ^ set2;
+
+  // now moving back the xor'd sets to p1 and p2
+  xorSets = (xorSets << p1) | (xorSets << p2);
+
+  unsigned int finalVal = xorSets ^ num;
+  return finalVal;
+}
+
+int main()
+{
+  std::cout << "Swaping bits in number 28, such that 2 bits starting from 0th bit and 2 bits "
+               "starting from 3rd bit are swapped, 28 becomes " << swapBits(28, 0, 3, 2)
+               << std::endl;
+
+  std::cout << "Swaping bits in number 47, such that 3 bits starting from 1st bit(0 based counting) and 3 bits "
+               "starting from 5th bit(0 based counting) are swapped, 47 becomes " << swapBits(47, 1, 5, 3)
+               << std::endl;
+}

graph_problems/bfsDemo.cpp

@@ -0,0 +1,29 @@
+#include <iostream>
+#include "graph.h"
+
+/**
+ * Implementation of BFS algorithm is in ../include/graph.h
+ */
+
+int main()
+{
+  std::vector<int> vec{ 0, 1, 2, 3, 4, 5, 6, 7 };
+  algo::Graph<int> g(vec);
+  g.setEdge(0, 1);
+  g.setEdge(0, 2);
+  g.setEdge(1, 0);
+  g.setEdge(1, 2);
+  g.setEdge(1, 3);
+  g.setEdge(2, 4);
+  g.setEdge(2, 6);
+  g.setEdge(3, 1);
+  g.setEdge(3, 7);
+  g.setEdge(4, 6);
+  g.setEdge(5, 1);
+  g.setEdge(5, 3);
+  g.setEdge(6, 5);
+  g.setEdge(7, 5);
+  g.display();
+  g.breadth_first_search(0);
+  return 0;
+}

graph_problems/dfsDemo.cpp

@@ -1,5 +1,10 @@
 #include <iostream>
-#include <graph.h>
+#include "graph.h"
+
+
+/**
+ * Implementation of BFS algorithm is in ../include/graph.h
+ */
 
 int main()
 {