Merge pull request #213 from vishakhaa05/patch-1

Add WildcardMatching class with isMatch method

Author: admirerr

Java/dynamic-programming/WildcardMatching.java

@@ -0,0 +1,58 @@
+public class WildcardMatching {
+
+    // Function to check if string s matches pattern p
+    public boolean isMatch(String s, String p) {
+        int n = s.length();
+        int m = p.length();
+
+        // DP table: dp[i][j] = does s[0..i-1] match p[0..j-1] ?
+        boolean[][] dp = new boolean[n + 1][m + 1];
+
+        // Base case: empty string matches empty pattern
+        dp[0][0] = true;
+
+        // Fill for patterns that start with '*'
+        // e.g., s = "" and p = "***" should be true
+        for (int j = 1; j <= m; j++) {
+            if (p.charAt(j - 1) == '*') {
+                dp[0][j] = dp[0][j - 1]; // '*' can represent empty string
+            }
+        }
+
+        // Fill the DP table
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= m; j++) {
+                char sc = s.charAt(i - 1); // current char in string
+                char pc = p.charAt(j - 1); // current char in pattern
+
+                if (pc == sc || pc == '?') {
+                    // If chars match OR '?' wildcard, carry forward diagonal
+                    dp[i][j] = dp[i - 1][j - 1];
+                } else if (pc == '*') {
+                    // '*' can represent:
+                    // 1. empty sequence -> dp[i][j-1]
+                    // 2. one or more characters -> dp[i-1][j]
+                    dp[i][j] = dp[i][j - 1] || dp[i - 1][j];
+                } else {
+                    dp[i][j] = false; // mismatch
+                }
+            }
+        }
+
+        // Answer is whether entire s matches entire p
+        return dp[n][m];
+    }
+
+    // ----------------------------
+    // Example Usage
+    // ----------------------------
+    public static void main(String[] args) {
+        WildcardMatching solver = new WildcardMatching();
+
+        System.out.println(solver.isMatch("aa", "a"));   // false
+        System.out.println(solver.isMatch("aa", "*"));   // true
+        System.out.println(solver.isMatch("cb", "?a"));  // false
+        System.out.println(solver.isMatch("adceb", "*a*b")); // true
+        System.out.println(solver.isMatch("acdcb", "a*c?b")); // false
+    }
+}