Create RegularExpressionMatching.cpp

https://leetcode.com/problems/regular-expression-matching/

Author: itsgauravsingh

RegularExpressionMatching.cpp

@@ -0,0 +1,108 @@
+class Solution {
+public:
+    bool recur(string& s,string& p, int& m, int& n, int i, int j) {
+		if(i>=m && j>=n)
+			return true;
+		if(i<m && j<n) {
+			if(j+1<n) {
+				if(p[j+1] == '*') {
+					return (recur(s,p,m,n,i,j+2) || ((s[i]==p[j] || p[j]=='.') ? recur(s,p,m,n,i+1,j) : false));
+				} 
+				return ((s[i]==p[j] || p[j]=='.') ? recur(s,p,m,n,i+1,j+1) : false);
+			}
+			if(s[i] == p[j] || p[j]=='.')
+				return (i == m-1);
+		}
+		if(i>=m && j<n) {
+			return isConsumable(p,j,n,s[m-1]);
+		}
+		return false;
+	}
+	bool isConsumable(string& p, int j,int n,char a) {
+		bool alt=false;
+		stack <char> s1;
+		if(p[j] == '*') {
+			alt = true;
+			j++;
+		}			
+		while(j<n){
+			if(p[j] != '*') {
+				s1.push(p[j]);
+			} else {
+				if(s1.empty())
+					return false;
+				s1.pop();
+			}
+			j++;
+		}
+		if(alt && s1.size() == 1 && s1.top() == a) {
+			return true;
+		}
+		if(s1.empty())
+			return true;
+		return false;
+	}
+    
+    bool isMatch(string s, string p) {
+        int m = s.length();
+        int n = p.length();
+        char prev = ' ';
+        int s_txt = 0;
+        int p_txt = 0;
+        int count = 0;
+        bool f = false;
+        int i=0,j=0,c=0;
+        if (!m && !n)
+            return true;
+        if(!n || p[0] == '*') {
+            cout<<"\nExiting due to pattern length";
+            return false;
+        }        
+        return recur(s,p,m,n,0,0);
+    }
+};
+
+string stringToString(string input) {
+    assert(input.length() >= 2);
+    string result;
+    for (int i = 1; i < input.length() -1; i++) {
+        char currentChar = input[i];
+        if (input[i] == '\\') {
+            char nextChar = input[i+1];
+            switch (nextChar) {
+                case '\"': result.push_back('\"'); break;
+                case '/' : result.push_back('/'); break;
+                case '\\': result.push_back('\\'); break;
+                case 'b' : result.push_back('\b'); break;
+                case 'f' : result.push_back('\f'); break;
+                case 'r' : result.push_back('\r'); break;
+                case 'n' : result.push_back('\n'); break;
+                case 't' : result.push_back('\t'); break;
+                default: break;
+            }
+            i++;
+        } else {
+          result.push_back(currentChar);
+        }
+    }
+    return result;
+}
+
+string boolToString(bool input) {
+    return input ? "True" : "False";
+}
+
+int main() {
+    string line;
+    while (getline(cin, line)) {
+        string s = stringToString(line);
+        getline(cin, line);
+        string p = stringToString(line);
+        
+        bool ret = Solution().isMatch(s, p);
+
+        string out = boolToString(ret);
+        cout << out << endl;
+    }
+    return 0;
+}