Indented "countingSort" and fixed compilation errors

Added description about advantage of counting sort over comparison sort and
how counting sort can be stabilized.

Author: r7919

sorting/countingSort.c

@@ -1,28 +1,36 @@
 #include <stdio.h>
-  int main()
- {
- 	int i,n,l=0;
-  scanf("%d",&n);
- 	int a[n];
-  for(i=0;i<n;i++)
- 	{
-  	 	scanf("%d",&a[i]);
-  	 	if(a[i]>l)
-  	 	 l=a[i];
- 	}
- 	int b[l+1]={0};
- 	for(i=0;i<n;i++)
+#include<string.h>
+/*
+  > Counting sort is a sorting technique based on keys between a specific range.
+  > integer sorting algorithm
+  > Worst-case performance O(n+k)
+  > Stabilized by prefix sum array
+*/
+int main()
+{
+   int i,n,l=0;
+   scanf("%d",&n);
+   int a[n];
+   for(i=0;i<n;i++)
+   {
+  	  scanf("%d",&a[i]);
+  	  if(a[i] > l)
+  	   l = a[i];
+   }
+   int b[l+1];
+   memset(b, 0, (l+1)*sizeof(b[0]));
+   for(i=0;i<n;i++)
  	 b[a[i]]++; //hashing number to array index
- 	for(i=0;i<(l+1);i++)
- 	{
- 		if(b[i]>0)
+    for(i=0;i<(l+1);i++) //unstable , stabilized by prefix sum array
  	{
- 			while(b[i]!=0) //for case when number exists more than once
- 			{
- 			printf("%d ",i); 
- 			b[i]--;
- 			}
-    	}
+ 	  if(b[i]>0)
+ 	  {
+ 		 while(b[i]!=0) //for case when number exists more than once
+ 		 {
+ 		   printf("%d ",i); 
+ 		   b[i]--;
+ 		 }
+       }
  	}
- 	return 0;
- } 
+  return 0;
+}