Computer_Science/leetcode/65-valid_number.c


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#include <string.h>

bool isNumber(char* s) {
	char *p;
	int dot_flag = 0;
	int e_flag = 0;

	for(; *s == ' '; s++)
		;
	if(*s == '+' || *s == '-')
		s++;

	p = s;

	/* trim tail */
	for(; *p != '\0'; p++)
		;
	for(p--; p != s && *p == ' '; p--)
		;
	*(p + 1) = '\0';

	p = s;
	if(*p == '\0') return false;
	
	for(; *p != '\0'; p++) {
		if(*p <= '9' && *p >= '0')
			continue;
		else if(*p == '.') {
			if(dot_flag == 1)
				return false;
			if((s == p && *(p + 1) == '\0')
			   || *(p - 1) == 'e')
				return false;
			dot_flag = 1;
			continue;
		} else if(*p == 'e') {
			if(e_flag == 1)
				return false;
			if(s == p || *(p + 1) == '\0' || (*(p - 1) == '.' && p - 1 == s))
				return false;
			e_flag = 1;
		} else
			return false;
	}

	return true;
}