// Source : https://oj.leetcode.com/problems/valid-number/
// Author : Hao Chen
// Date : 2014-08-26
/**********************************************************************************
*
* 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.
*
*
**********************************************************************************/
#include
using namespace std;
bool isdigit(const char c){
return (c>='0' && c<='9');
}
bool isspace(const char c) {
return (c==' ' || c =='\t' || c=='\n' || c=='\r' || c=='\f' || c=='\v');
}
bool isNumber(const char *s) {
bool point = false;
bool hasE = false;
//trim the space
while(isspace(*s)) s++;
//check empty
if (*s == '\0' ) return false;
//check sign
if (*s=='+' || *s=='-') s++;
const char *head = s;
for(; *s!='\0'; s++){
// if meet point
if ( *s == '.' ){
if ( hasE == true || point == true){
return false;
}
if ( s == head && !isdigit(*(s+1)) ){
return false;
}
point = true;
continue;
}
//if meet "e"
if ( *s == 'e' ){
if ( hasE == true || s == head) {
return false;
}
s++;
if ( *s=='+' || *s=='-' ) s++;
if ( !isdigit(*s) ) return false;
hasE = true;
continue;
}
//if meet space, check the rest chars are space or not
if (isspace(*s)){
for (; *s != '\0'; s++){
if (!isspace(*s)) return false;
}
return true;
}
if ( !isdigit(*s) ) {
return false;
}
}
return true;
}
#define TEST(s) cout << "\"" << s << "\"" << " : " << isNumber(s) << endl
int main(int argc, char** argv)
{
const char* s="123";
if(argc>1){
s = argv[1];
}
TEST(s);
TEST("1.044");
TEST(" 1.044 ");
TEST("1.a");
TEST("abc");
TEST("e");
TEST("1e");
TEST("1e2");
TEST("");
TEST(" ");
TEST("1.");
TEST(".2");
TEST(" . ");
TEST(".");
TEST("1.2.3");
TEST("1e2e3");
TEST("1..");
TEST("+1.");
TEST(" -1.");
TEST("6e6.5");
TEST("005047e+6");
return 0;
}