#include <stdio.h>
#include <string.h>

int main() {
	int i;
	char input_string[80];
	char search_chr, replace_chr;

	printf("Input a string:\n");
	fgets(input_string, sizeof(input_string), stdin);

	printf("Input a character to replace: ");
	char search_string[80];
	fgets(search_string, sizeof(search_string), stdin);
	search_chr = search_string[0];

	printf("Input a replacement character: ");
	char replace_string[80];
	fgets(replace_string, sizeof(replace_string), stdin);
	replace_chr = replace_string[0];

	if (strrchr(input_string, search_chr) != NULL) {
		for (i=0; input_string + i != strrchr(input_string, search_chr); i++);
		*(input_string + i) = replace_chr;
	}

	printf("Updated: %s", input_string);
	printf("Character to replace: %c\n", search_chr);
	printf("Replacement character: %c\n", replace_chr);
}

#include <stdio.h>
#include <string.h>

int main() {
	char *cptr;
	char input_string[80];
	char search_chr, replace_chr;

	printf("Input a string:\n");
	fgets(input_string, sizeof(input_string), stdin);

	printf("Input a character to replace: ");
	char search_string[80];
	fgets(search_string, sizeof(search_string), stdin);
	search_chr = search_string[0];

	printf("Input a replacement character: ");
	char replace_string[80];
	fgets(replace_string, sizeof(replace_string), stdin);
	replace_chr = replace_string[0];

	cptr = strrchr(input_string, search_chr);
	if (cptr) {
		*cptr = replace_chr;
	}

	printf("Updated: %s", input_string);
	printf("Character to replace: %c\n", search_chr);
	printf("Replacement character: %c\n", replace_chr);
}