chore(CPlusPlus): add index of smallest element in array (#584)

Co-authored-by: Ming Tsai <37890026+ming-tsai@users.noreply.github.com>

algorithms/CPlusPlus/Arrays/index-of-smallest-element-of-array.cpp

@@ -0,0 +1,35 @@
+//index of smallest element of array
+/* Example :
+size of array =5
+Let array be ,arr[5]={9,4,1,5,8}
+here smallest element of array is 1 which is at index 2 of array 
+output = 2 that is index of smallest element of array.
+Time complexity = O(n)
+*/
+
+#include<iostream>
+using namespace std;
+int main()
+{
+    int size,j;
+    cout<<"enter the size of array";
+    cin>>size;
+    int arr[size];
+    for(int i=0;i<size;i++)
+    {
+        cin>>arr[i];
+    }
+    //considering the element at zero index to be smallest
+    int min=arr[0];
+    int smallest_index=0;
+    //comparing min to all other elements
+    for(j=0;j<size;j++)
+    {
+        if(min>arr[j])
+        {
+            min=arr[j];
+            smallest_index=j;
+        }
+    }
+    cout<<"index of smallest element of array is"<<smallest_index;
+}

algorithms/CPlusPlus/README.md

@@ -22,6 +22,7 @@
 - [Matrix Multiplication](Arrays/matrix-multiplication.cpp)
 - [Smallest Sum Possible](Arrays/smallest-sum-possible.cpp)
 - [Smallest Possible Sum](Arrays/smallest-possible-sum.cpp)
+- [Index of Smallest element of Array](Arrays/index-of-smallest-element-of-array.cpp)
 - [Move Zeros to End of The Array](Arrays/move-zeros-to-end-of-array.cpp)
 - [Kadane's Algorithm](Arrays/Kadane's-Algorithm.cpp)