Added find common in 3 vectors.

Author: Ravi Mandliya

README.md

@@ -6,8 +6,8 @@
 
 | Current Status|     Stats     |
 | :------------: | :----------: |
-| Total Problems | 135 |
-| Current Streak | 5 days |
+| Total Problems | 136 |
+| Current Streak | 6 days |
 | Longest Streak | 91 ( August 17, 2015 - November 15, 2015 ) |
 
 </center>
@@ -170,6 +170,7 @@ Include contains single header implementation of data structures and some algori
 | Given an array A of n elements, find three indices i, j and k such that A[i]^2 + A[j]^2 = A[K]^2. O(n2) time complexity and O(1) space complexity | [squareSum.cpp](sort_search_problems/squareSum.cpp)|
 | Given an unsorted array arr[0..n-1] of size n, find the minimum length subarray arr[s..e] such that sorting this subarray makes the whole array sorted. |[minLengthUnsortedArray.cpp](sort_search_problems/minLengthUnsortedArray.cpp)|
 | Find the missing number in Arithmetic Progression | [missingNumber2.cpp](sort_search_problems/missingNumber2.cpp) |
+| Find the common elements in 3 sorted arrays | [commonIn3Arrays.cpp](sort_search_problems/commonIn3Arrays.cpp) |
 ### Graph Problems
 | Problem | Solution |
 | :------------ | :----------: |

sort_search_problems/commonIn3Arrays.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <vector>
+
+void printCommonElements(const std::vector<int>& vec1,
+                         const std::vector<int>& vec2,
+                         const std::vector<int>& vec3)
+{
+    std::vector<int>::const_iterator it1 = vec1.begin();
+    std::vector<int>::const_iterator it2 = vec2.begin();
+    std::vector<int>::const_iterator it3 = vec3.begin();
+
+    while (it1 != vec1.end() && it2 != vec2.end() && it3 != vec3.end())
+    {
+        if (*it1 == *it2 && *it2 == *it3)
+        {
+            std::cout << *it1 << " ";
+            it1++;
+            it2++;
+            it3++;
+        }
+        else if (*it1 < *it2)
+        {
+            ++it1;
+        }
+        else if (*it2 < *it3)
+        {
+            ++it2;
+        }
+        else
+        {
+            ++it3;
+        }
+    }
+    std::cout << std::endl;
+}
+
+
+int main()
+{
+    std::vector<int> vec1 {2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
+    std::vector<int> vec2 {3, 6, 9, 12, 15, 18, 21};
+    std::vector<int> vec3 {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20};
+
+    printCommonElements(vec1, vec2, vec3);
+    return 0;
+}