#include <iostream>
#include <string.h>using namespace std;void scanDigits(char** string){while(**string!='\0' && **string>='0' && **string<='9')++(*string);
}bool isExponential(char** string){if(**string!='e' && **string!='E')return false;++(*string);if(**string=='+' || **string=='-')++(*string);if(**string=='\0')return false;scanDigits(string);return (**string=='\0')?true:false;
}bool isNumeric(char* string){if(string==NULL)return false;if(*string=='+' || *string=='-')++string;if(*string=='\0')return false;bool numeric=true;scanDigits(&string);if(*string!='\0'){if(*string=='.'){++string;scanDigits(&string);if(*string=='e' || *string=='E')numeric=isExponential(&string);}else if(*string=='e' || *string=='E')numeric=isExponential(&string);elsenumeric=false;}return numeric && *string=='\0';
}int main()
{cout << isNumeric("5e2") << endl;cout << isNumeric("12e") << endl;cout << isNumeric("1a3.14") << endl;cout << isNumeric("+-5") << endl;return 0;
}

class Solution {
public:bool isNumeric(char* string){if(string==NULL)return false;int len=strlen(string);int index=0;if(string[index]=='+' || string[index]=='-')++index;if(index>=len)return false;bool numeric=true;scanDigit(string,index);if(index<len){if(string[index]=='.'){++index;scanDigit(string,index);if(index>=len)numeric=true;else if(string[index]=='e' || string[index]=='E')numeric=isExponential(string,index);elsenumeric=false;}else if(string[index]=='e' || string[index]=='E')numeric=isExponential(string,index);elsenumeric=false;}return numeric;      }void scanDigit(char* string,int& index){while(string[index]!='\0' && string[index]>='0' && string[index]<='9')++index;}bool isExponential(char* string,int index){if(string[index]!='e' && string[index]!='E')return false;++index;if(string[index]=='+' || string[index]=='-')++index;if(string[index]=='\0')return false;scanDigit(string,index);return (string[index]=='\0')?true:false;}};