added doc on 2-d arrays

Data Structures/Arrays/2-D arrays.md

@@ -0,0 +1,103 @@
+Introduction:
+2D array is an array of arrays. In this we store data in tabular form, rows and columns. 
+Syntax: datatype [size][size]
+Example:- int twodarr[4][4];
+
+Size of array: 
+When you multiply the size of an array you can store that number of values in the 2D array. 
+Example: int arr[3][3];
+In this example multiply 3x3=9, so you can store 9 elements in the array.
+
+Initializing the 2-D array:
+Method 1:
+int a[4][4] = {  
+   {2,4,6,8} ,   /* values of row indexed 0 */
+   {1,2,3,4} ,   /* values of row indexed 1 */
+   {9,8,7,11},   /*  values of row indexed 2 */
+   {4,8,10,5} /*  values of row indexed 3 */
+};
+
+Method 2:
+int a[4][3] = {0,1,2,3,4,5,6,7,8,9,10,11};
+
+Access the elements of an array:
+We make use of row number and column number to access the elements. 
+Example: 
+int a[4][4] = {  
+   {2,4,6,8} ,  
+   {1,2,3,4} ,   
+   {9,8,7,11}, 
+   {4,8,10,5} 
+};
+int val = a[3][3];
+This is return 5 by moving rowwise 0-3 an columnwise 0-3
+
+Code:
+#include <iostream>
+
+using namespace std; 
+int main () {
+
+   // an array of 4 rows and 3 columns.
+   int a[4][3] = { {0,4,5}, {1,2,3}, {2,4,9}, {3,6,8}};
+ // output will be 2nd element from 3rd row                            
+         cout << a[3][2]: ;
+
+   return 0;
+}
+
+Output :
+8
+// As the array indexing starts from 0 we have 0 to 3 rows and 0 to 2 columns
+
+Method to enter data to a 2-D array
+Nested loops can be used to enter the elements in the array. We can use for loop or while depending upon the requirement.
+
+#include<iostream>
+using namespace std;
+
+int main()
+{ 
+int matrix [5] [4];
+for (int mat1=0 ; mat1<5 ; mat1++)
+{
+for (int mat2=0 ; mat2<4 ; mat2++)
+{
+matrix [m1] [m2] ;
+}
+}
+}
+
+Initializing the 2-D character array:
+Write char instead of int at the time of initialization. 
+Example:
+char array[4] [3]= { 'm', 'a', 'n' ,
+'b', 'a', 'n' ,
+'g', 'r', 't' 
+‘a’,’n’,’d’};
+
+Code:
+#include <iostream>
+
+int main()
+{
+    // Initialize 2D array
+    char array[5] [10]= { "man", "pot", "van", "run"};
+
+
+    // Printing Strings stored in 2D array
+    for (int i = 0; i < 4; i++)
+        std::cout << array[i] << "\n";
+
+    return 0;
+}
+
+Output:
+man
+pot
+van
+run
+
+
+Summary:
+It has become easy to store values in variables with the help of arrays.