Added Wildcard_Matching.cpp

Author: Spider-50140

CPP/dynamic_programming/Wildcard_Matching.cpp

@@ -0,0 +1,104 @@
+/*
+ * Wildcard Matching Algorithm
+ * 
+ * Description:
+ * Given an input string (s) and a pattern (p), implement wildcard pattern matching with support for:
+ * - '?' Matches any single character
+ * - '*' Matches any sequence of characters (including the empty sequence)
+ * 
+ * The matching should cover the entire input string (not partial).
+ *
+ * Approach:
+ * We use recursion with the following rules:
+ * 1. If both string and pattern are exhausted, return true.
+ * 2. If pattern is exhausted but string remains, return false.
+ * 3. If string is exhausted but pattern remains, check if remaining characters in pattern are all '*'.
+ * 4. If characters match OR pattern has '?', move both indices back by 1.
+ * 5. If pattern has '*', try two options:
+ *      - Treat '*' as matching one character (move string index back by 1, keep pattern index same).
+ *      - Treat '*' as matching empty (move pattern index back by 1, keep string index same).
+ *
+ * Time Complexity: Exponential in worst case (O(2^(m+n))) without memoization,
+ *                  since '*' can branch into two recursive calls.
+ *                  With DP memoization, this can be optimized to O(m*n).
+ *
+ * Space Complexity: O(m+n) recursion stack (without memoization).
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    bool solve(int index1, int index2, string &text, string &pattern) {
+        // Both strings exhausted
+        if (index1 < 0 && index2 < 0) return true;
+
+        // Pattern exhausted, text remains
+        if (index2 < 0 && index1 >= 0) return false;
+
+        // Text exhausted, check if remaining pattern is all '*'
+        if (index1 < 0 && index2 >= 0) {
+            for (int i = 0; i <= index2; i++) {
+                if (pattern[i] != '*') return false;
+            }
+            return true;
+        }
+
+        // Characters match OR pattern has '?'
+        if (text[index1] == pattern[index2] || pattern[index2] == '?') {
+            return solve(index1 - 1, index2 - 1, text, pattern);
+        }
+
+        // If pattern has '*': try both possibilities
+        if (pattern[index2] == '*') {
+            return solve(index1 - 1, index2, text, pattern)   // '*' matches one char
+                || solve(index1, index2 - 1, text, pattern); // '*' matches empty
+        }
+
+        return false;
+    }
+
+    bool isMatch(string s, string p) {
+        int n1 = s.size();
+        int n2 = p.size();
+        return solve(n1 - 1, n2 - 1, s, p);
+    }
+};
+
+// Main function with test cases
+int main() {
+    Solution sol;
+
+    // Test Case 1
+    cout << "Test Case 1:" << endl;
+    string s1 = "aa", p1 = "a";
+    cout << "String: " << s1 << ", Pattern: " << p1 << endl;
+    cout << "Match: " << (sol.isMatch(s1, p1) ? "true" : "false") << endl << endl; // false
+
+    // Test Case 2
+    cout << "Test Case 2:" << endl;
+    string s2 = "aa", p2 = "*";
+    cout << "String: " << s2 << ", Pattern: " << p2 << endl;
+    cout << "Match: " << (sol.isMatch(s2, p2) ? "true" : "false") << endl << endl; // true
+
+    // Test Case 3
+    cout << "Test Case 3:" << endl;
+    string s3 = "cb", p3 = "?a";
+    cout << "String: " << s3 << ", Pattern: " << p3 << endl;
+    cout << "Match: " << (sol.isMatch(s3, p3) ? "true" : "false") << endl << endl; // false
+
+    // Test Case 4
+    cout << "Test Case 4:" << endl;
+    string s4 = "adceb", p4 = "*a*b";
+    cout << "String: " << s4 << ", Pattern: " << p4 << endl;
+    cout << "Match: " << (sol.isMatch(s4, p4) ? "true" : "false") << endl << endl; // true
+
+    // Test Case 5
+    cout << "Test Case 5:" << endl;
+    string s5 = "acdcb", p5 = "a*c?b";
+    cout << "String: " << s5 << ", Pattern: " << p5 << endl;
+    cout << "Match: " << (sol.isMatch(s5, p5) ? "true" : "false") << endl << endl; // false
+
+    return 0;
+}