Regular Expression Matching

正则匹配

Regular Expression Matching

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

package com.rust.TestString;

class Solution {
public boolean isMatch(String s, String p) {
if (p.length() == 0) {
return s.length() == 0;
}
if (p.length() == 1) {
return (s.length() == 1) && (p.charAt(0) == s.charAt(0) || p.charAt(0) == '.');
}
// next char is not '*': must match current character
if (p.charAt(1) != '*') {
if (s.length() == 0) {
return false;
} else {
return (s.charAt(0) == p.charAt(0) || p.charAt(0) == '.')
&& isMatch(s.substring(1), p.substring(1));  // judge next char
}
} else {    // next char is '*'
while (s.length() > 0 && (p.charAt(0) == s.charAt(0) || p.charAt(0) == '.')) {
if (isMatch(s, p.substring(2))) {
return true;
}
s = s.substring(1);
}
return isMatch(s, p.substring(2));
}
}
}

public class RegularExpressionMatching {
public static void main(String args[]){
Solution solution = new Solution();
String s = "abcdefg";
System.out.println(solution.isMatch(s, "abcde*"));
System.out.println(solution.isMatch(s, ".*"));
System.out.println(solution.isMatch("abcdefg", "a.*"));
System.out.println(solution.isMatch("abcdefg", ".b."));
System.out.println(solution.isMatch("abcdefg", ""));
System.out.println(s);
}
}

输出：

false
true
true
false
false
abcdefg