regular expression matching

Leetcode/regular.txt

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    int dp[21][31];
+    bool func(int i,int j,string &s,string &p){
+        if(dp[i][j] != -1) return dp[i][j];
+        if(i >= s.size()){
+            if(j == p.size()) return dp[i][j] = true;
+            if(j + 1 < p.size() && p[j + 1] == '*') return dp[i][j] = func(i,j + 2,s,p);
+            return dp[i][j] = false;
+        }
+        else if(j == p.size()) return dp[i][j] = false;
+        bool match = (s[i] == p[j] || p[j] == '.');
+        bool ans = false;
+        if(match){
+            if(j + 1 < p.size() && p[j + 1] == '*') ans = func(i+1,j,s,p);
+            if(!ans) ans = func(i + 1,j + 1,s,p);
+        }
+        if(!ans && j + 1 < p.size() && p[j + 1] == '*') ans = func(i,j + 2,s,p);
+        return dp[i][j] = ans;
+    }
+    bool isMatch(string s, string p) {
+        memset(dp,-1,sizeof dp);
+        return func(0,0,s,p);
+    }
+};