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
Solution:
public class Solution {
public boolean isMatch(String s, String p) {
int n = s.length(), m = p.length();
boolean[][] dp = new boolean[n + 1][m + 1];
// initialize
dp[0][0] = true;
for (int j = 1; j <= m; j++)
dp[0][j] = j > 1 && p.charAt(j - 1) == '*' && dp[0][j - 2];
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (p.charAt(j - 1) != '*')
dp[i][j] = dp[i - 1][j - 1] && isMatch(s.charAt(i - 1), p.charAt(j - 1));
else
dp[i][j] = dp[i][j - 2] || dp[i - 1][j] && isMatch(s.charAt(i - 1), p.charAt(j - 2));
}
}
return dp[n][m];
}
boolean isMatch(char a, char b) {
return a == b || b == '.';
}
}