065 - Valid Number

Validate if a given string is numeric.

Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts aconst char * argument, please click the reload button to reset your code definition.

enum numtype {NOTNUM = 0,INTNUM,POINUM,};enum numtype checknum(char *numstr){int len, i, ret = INTNUM;if (*numstr == '-' || *numstr == '+')numstr++;len = strlen(numstr);if (!len)return NOTNUM;for (i = 0; i < len; i++) {if (!isdigit(numstr[i]) && numstr[i] != '.')return NOTNUM;if (numstr[i] == '.') {if (ret == POINUM || !i && !isdigit(numstr[i + 1]))return NOTNUM;elseret = POINUM;}}return ret;}bool isNumber(char* s){int slen = strlen(s);char *end = s + slen - 1;char *begin = s;while (end - s > 0 && *end == ' ')*end-- = '\0';while (*begin == ' ')*begin++ = '\0';if (!*begin)return 0;s = begin;char *ep = strchr(s, 'e');if (!ep)return checknum(s) == NOTNUM ? 0 : 1;*ep = '\0';if (checknum(s) != NOTNUM && checknum(ep + 1) == INTNUM)return 1;return 0;}

test data

12.12-13.2312.12e812.12e8.1-13.23e-8.1           (true)3.           (true). 0