gistfile1.txt

//str_len

#include <stdio.h>
int strlen(char*s){
  int length=0;
  while(s[length])
    ++length;
  return length;
}
int main(){
  char *s="Hello 0123!";
  printf("字串'%s'的長度為'%d'\n", s, strlen(s));
  return 0;
}

修正的東西

bool strneq(char *p, char *q, int n){
  int i=0;
  while( (*p||*q) && i++<n ){
    if(*p!=*q)
      return false;
      p++;
      q++;
    }
  return true;
}
int main() {
    char s1[]="AB";
    char s2[]={'A', 0, 'A', 'C', 0};
    bool cond=strneq(s1, s2, 2);
    cond=strneq(s1, s2+2, 1);
    return 0;
}

兩字串是否相等

bool streq(char *p, char *q){
  while(*p||*q)
  if(*p++!=*q++)
    return false;
return true;
}
int main() {
  char s1[]="AB";
  char s2[]={'A', 0, 'A', 'B', 0};
  bool cond=streq(s1, s2);
  cond=streq(s1, s2);
  streq(s1, s2+2);
  return 0;
}

前n個字元是否相等

bool strneq(char *p, char *q, int n){
  int i=0;
  while( *p||*q && i++<n ) // short-cut evaluation if(*p++!=*q++)
    return false;
  return true;
}
int main() {
  char s1[]="AB";
  char s2[]={'A', 0, 'A', 'C', 0};
  bool cond=strneq(s1, s2, 1); cond=strneq(s1, s2+2, 1);
  return 0;
}

字串中有幾個ch字元

// #'0' char
#include <stdio.h>
int char_count(char*str, char ch){
	int count=0;
	for(int i=0; str[i]!=0; ++i)
		if(str[i]==ch)
			++count;
	return count;
}
int main(){

	char *s="Hello 0123!";
	printf("'%s'裡面有'%d'個'%c'字元\n", s, char_count(s,'0'), '0');
	return 0;
}

字串中有幾個數字字元

//#digit

#include <stdio.h>
int digit_count(char*str){
	int count=0;
	for(int i=0; str[i]; ++i)
		if(str[i]>='0' && str[i]<='9')
			++count;
return count;
}
int main(){
	char *s="Hello 0123!";
	printf("'%s'裡有%d個數字字元\n",` s, digit_count(s));
	return 0;
}

``
//#digit

#include <stdio.h>
int digit_count(char*str){
int count=0;
for(int i=0; str[i]; ++i)
if(str[i]>='0' && str[i]<='9')
++count;
return count;
}
int main(){
char *s="Hello 0123!";
printf("'%s'裡有%d個數字字元\n",` s, digit_count(s)); return 0;
}
``

``
// all are digit

#include <stdio.h>
int are_all_digit(char*str){
for(int i=0; str[i]; ++i)
if(! (str[i]>='0' && str[i]<='9'))
return 0;
return *str?1:0;

}
int main(){
char *s="Hello 0123!";
printf("'%s'裡全部都是字元? %D\n",s,are_all_digit(s));
return 0;
}

``