【leetcode】Valid Number

Question ： 

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.

Anwser 1 ：     

class Solution {public:    bool isNumber(const char *s) {        // Start typing your C/C++ solution below        // DO NOT write int main() function                if (s == NULL)             return false;                      while(isspace(*s))             s++;                      if (*s == '+' || *s == '-')             s++;                      bool eAppear = false;         bool dotAppear = false;         bool firstPart = false;         bool secondPart = false;         bool spaceAppear = false;         while(*s != '\0')         {             if (*s == '.')             {                 if (dotAppear || eAppear || spaceAppear)                     return false;                 else                     dotAppear = true;             }             else if (*s == 'e' || *s == 'E')             {                 if (eAppear || !firstPart || spaceAppear)                     return false;                 else                     eAppear = true;             }             else if (isdigit(*s))             {                 if (spaceAppear)                     return false;                                      if (!eAppear)                     firstPart = true;                 else                     secondPart = true;             }             else if (*s == '+' || *s == '-')   // behind of e/E             {                 if (spaceAppear)                     return false;                                      if (!eAppear || !(*(s-1) == 'e' || *(s-1) == 'E'))                     return false;             }             else if (isspace(*s))                 spaceAppear = true;             else                 return false;                              s++;                     }                  if (!firstPart) {             return false;         }  else if (eAppear && !secondPart) {             return false;         }          return true;      }};

Anwser 2 ：     

class Solution {public:    bool isNumber(const char *s) {        // Start typing your C/C++ solution below        // DO NOT write int main() function                int mat[11][7] = {                      0 ,0 ,0 ,0 ,0 ,0 ,0,      // false                      0 ,2 ,3 ,0 ,1 ,4 ,0,      // 1                      0 ,2 ,5 ,6 ,9 ,0 ,10,     // 2                      0 ,5 ,0 ,0 ,0 ,0 ,0,      // 3                      0 ,2 ,3 ,0 ,0 ,0 ,0,      // 4                      0 ,5 ,0 ,6 ,9 ,0 ,10,     // 5                      0 ,7 ,0 ,0 ,0 ,8 ,0,      // 6                      0 ,7 ,0 ,0 ,9 ,0 ,10,     // 7                      0 ,7 ,0 ,0 ,0 ,0 ,0,      // 8                      0 ,0 ,0 ,0 ,9 ,0 ,10,     // 9                      10,10,10,10,10,10,10      // 10                    };                            int i = 0;        int stat = 1;        while(s[i] != '\0')         {            int type = 0;            if(s[i] >= '0' && s[i] <= '9')                type = 1;            else if(s[i] == '.')                type = 2;            else if(s[i] == 'e')                type = 3;            else if(s[i] == ' ')                type = 4;            else if(s[i] == '+' || s[i] == '-')                type = 5;            if(stat == 0)                return false;                            stat = mat[stat][type];            i++;        }        stat = mat[stat][6];        if(stat == 10) {            return true;        }                return false;    }};

參考推薦：

Valid Number