LeetCode 10 Regular Expression Matching （正则表达式匹配）

翻译

实现支持“.”和“*”的正则表达式匹配。

“.” 匹配支持单个字符
“*” 匹配零个或多个前面的元素

匹配应该覆盖到整个输入的字符串（而不是局部的）。

该函数的原型应该是：

bool isMatch(const char * s, const char * p)

示例：

isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true

原文

Implement regular expression matching with support for ‘.‘ and ‘*‘.

‘.‘ Matches any single character.
‘*‘ Matches zero or more of the preceding element.

The matching should cover the entire input string (not partial).

The function prototype should be:
bool isMatch(const char *s, const char *p)

Some examples:
isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true

C#，递归

public class Solution
{
    public bool IsMatch(string s, string p)
    {
        if (p.Length == 0)
            return s.Length == 0;

        if (p.Length == 1)
            return (s.Length == 1) && (p[0] == s[0] || p[0] == ‘.‘);

        if (p[1] != ‘*‘)
        {
            if (s.Length == 0)
                return false;
            else
                return (s[0] == p[0] || p[0] == ‘.‘)
                       && IsMatch(s.Substring(1), p.Substring(1));
        }
        else
        {
            while (s.Length > 0 && (p[0] == s[0] || p[0] == ‘.‘))
            {
                if (IsMatch(s, p.Substring(2)))
                    return true;
                s = s.Substring(1);
            }
            return IsMatch(s, p.Substring(2));
        }
    }
}