diff --git a/challenge_12/c/karanchawla/README.md b/challenge_12/c/karanchawla/README.md
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+```
+Karan Chawla
+Challenge #12
+```
+
+## Approach
+Implemented a counter array to count the occurence of each character in the input string and returned the output in the
+given format to the console. 
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diff --git a/challenge_12/c/karanchawla/challenge_12.c b/challenge_12/c/karanchawla/challenge_12.c
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+/*
+Karan Chawla
+Challenge 12
+*/
+
+#include <stdio.h> 
+#include <stdlib.h> 
+#include <string.h> 
+
+#ifndef MAX
+#define MAX 256
+#endif
+
+
+//function that counts the ocurrence of each element in the string
+void zip(const char *a, size_t size)
+{
+	int count[MAX] = { 0 };
+	int flag[MAX];
+
+	for(int i=0;i<size;i++)
+	{
+		count[(int)(a[i])]++;
+		flag[(int)(a[i])] = 1;
+	}
+	
+	//for(int i=0; i<MAX; i++) printf("%d ", flag[i]);
+	//if there's multiple occurences of chars
+	for(int i=0 ; i<size; i++)
+	{
+		if(count[(int)a[i]]>1 && flag[(int)a[i]]==1)
+		{
+			printf("%c#%d",a[i],count[(int)a[i]]);
+			flag[a[i]]=0;
+		}
+		else if(count[(int)a[i]]==1)
+			printf("%c",a[i]);
+	}
+
+	return;
+}
+
+//driver program
+int main(void)
+{
+	//example 1
+	const char *str = "The quick brown fox jumped over the lazy dog.";
+	size_t size = strlen(str);
+
+	//function call to zip
+	zip(str,size);
+
+	return 0;
+}
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