c语言十六进制转为十进制

#include <stdio.h>
#include <string.h>
int f(char arr []){
	int sum=0;
	for(int i=0;i<strlen(arr);i++){
		if(arr[i]>='0'&&arr[i]<='9'){
			arr[i]=arr[i]-'0';
		}
		else if(arr[i]>='a'&&arr[i]<='f'){
			arr[i]=arr[i]-'a'+10;
		}
		else if(arr[i]>='A'&&arr[i]<='F'){
			arr[i]=arr[i]-'A'+10;
		}
			sum=sum*16+arr[i]; 
		
			
	}
		printf("%d\n",sum);


	
	
}
int main(){
char a[3];
scanf("%s",a);
   f(a);
return 0;
}