剑指offer——21正则表达式匹配

 1 class Solution {
 2 public:
 3     bool match(char* str, char* pattern)
 4     {
 5         if (str == nullptr || pattern == nullptr)return false;
 6         return matchCore(str, pattern);
 7     }
 8     bool matchCore(const char *str, const char *pattern)
 9     {
10         if (*str == ‘\0‘ && *pattern == ‘\0‘)return true;
11         if (*str != ‘\0‘&& *pattern == ‘\0‘)return false;
12         if (*(pattern + 1) == ‘*‘)
13         {
14             if (*pattern == *str || (*pattern == ‘.‘ && *str != ‘\0‘))
15                 return matchCore(str + 1, pattern + 2) || //移动到下一个位置
16                 matchCore(str + 1, pattern) || // 待在自己的位置不动
17                 matchCore(str, pattern + 2);//忽略一个‘*’
18             else
19                 return matchCore(str, pattern + 2);//忽略一个‘*‘
20         }
21         if (*str == *pattern || (*pattern == ‘.‘ && *str != ‘\0‘))
22             return matchCore(str + 1, pattern + 1);
23         return false;
24     }
25 };