Regular Expression Match

Author: sawlani1234

Dynamic Programming/Regular Expression Match.txt

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+//Regex Matching with support for '?' and '*' for Strings A and Strings B
+// 1) �?� : Matches any single character.
+// 2) �*� : Matches any sequence of characters (including the empty sequence)
+
+
+#include<bits/stdc++.h>
+using namespace std;
+
+
+int dp[10000][200];// to store value of each state
+string s1,s2;
+
+bool rec(int i,int j)
+{
+    bool ans=false;
+    if(dp[i][j]!=-1)
+    return dp[i][j];
+    if(i==s1.length()&&j==s2.length()) //  edge case
+    return true;
+    if(i>s1.length()||j>=s2.length())
+    return false;
+
+   // Now visiting all possible states
+    if(s2[j]=='?')
+    {
+        ans=ans|rec(i+1,j+1);
+    }
+    else if(s2[j]=='*')
+    {
+        ans=ans|rec(i+1,j);
+        ans=ans|rec(i+1,j+1);
+        ans=ans|rec(i,j+1);
+    }
+    else if(s1[i]==s2[j])
+    {
+        ans=ans|rec(i+1,j+1);
+
+    }
+    return dp[i][j]=ans;
+}
+
+int isMatch(string A,string B)
+{
+    s1=A;
+    s2=B;
+    memset(dp,-1,sizeof(dp));
+    return rec(0,0);
+
+
+}
+
+int main()
+{
+    string a,b;
+    cout << "Enter first String " <<  endl;
+    cin >>  a;
+
+    cout << "Enter second String " <<  endl;
+    cin >>  b;
+
+      if(isMatch(a,b))
+        cout <<  "Both String Match" <<  endl;
+      else
+        cout << "Both String does not Match" <<  endl;
+
+
+}
+// Time Complexity : O(len(a)*len(b)) where len(x) is length of string x
+// Space Complexity : O(len(a)*len(b)) where len(x) is length of string x
+