コード:

#include <stdio.h>

#define X12(x) x,x,x,x,x,x,x,x,x,x,x,x
#define X13(x) X12(x),x
#define X18(x) X13(x),x,x,x,x,x
#define X69(x) X18(x),X18(x),X18(x),X13(x),x,x

char dfa[6][128] = {  // Deterministic Finite Automaton
	// \0..D, E,  F..Q,  R,  S..d,  e,  f..q,  r,  s..\177
	{ X69(0), 2, X12(0), 0, X18(0), 2, X12(0), 0, X13(0) },  // 0
	{ X69(0), 1, X12(0), 4, X18(0), 1, X12(0), 4, X13(0) },  // 1
	{ X69(1), 3, X12(1), 1, X18(1), 3, X12(1), 1, X13(1) },  // 2
	{ X69(1), 3, X12(1), 5, X18(1), 3, X12(1), 5, X13(1) },  // 3
};                                                        // 4, 5

int main(void)
{
	char s[256];
	while (1) {
		printf("Input a string:");
		if (!fgets(s, sizeof(s), stdin) || *s == '\n') break;
		int n = 0, t = 0, i = 0;
		while (s[i]) (t = dfa[t][s[i++]]) > 3 && (n++, t -= 4);
		printf("The total number of e*r is %d.\n", n);
	}
	return 0;
}

コード:

#include <stdio.h>
int main(void)
{
	char str[20 + 2] = "";

	printf("Input a string:");
	fgets(str, sizeof(str) ,stdin);
	
	int i;
	int er=0;
	
	for(i=2;str[i]!='\0';i++){
		if( (str[i - 2] == 'e' || str[i - 2] == 'E') && (str[i] == 'r' || str[i] == 'R') ){
			er += 1;
		}
	}
	
	printf("The total number of e*r is %d.\n", er);
	
	return 0;
}

コード:

#include <stdio.h>
int main(void)
{
	char str[20];

	printf("Input a string: ");
	fgets(str, 20 ,stdin);
	
	int i;
	int e=0;
	int r=0;
	
	for(i=0;i<20;i++){
		if( str[i] = 'e' ){
			e += 1;
		}
		if( str[i] = 'r' ){
			r += 1;
		}
	}
	
	int er;
	if(e <= r){
		er = e;
	}
	else{
		er = r;
	}
	
	printf("The total number of e*r is %d.\n", er);
	
  return 0;
}