Leetcode-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

DP

bool isMatch(string s, string p) {
int sl=s.length();
int pl=p.length();

vector<vector<bool>> dp(pl+1,vector<bool>(sl+1,false));
dp[0][0]=true;

for(int i=1;i<=pl;++i)
{
dp[i][0]=i-2>=0&&p[i-1]=='*'&&dp[i-2][0];
for(int j=1;j<=sl;++j)
{
if(p[i-1]==s[j-1]||p[i-1]=='.')
{
dp[i][j]=dp[i-1][j-1];
}
else if(p[i-1]=='*'&&i-2>=0)
{
if(dp[i-2][j]||((p[i-2]==s[j-1]||p[i-2]=='.')&&dp[i][j-1]))
{
dp[i][j]=true;
}
else
{
dp[i][j]=false;
}
}
else
{
dp[i][j]=false;
}

}

}
return dp[pl][sl];

}