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📝 Today's Problem Text: "HELLO WORLD HELLO" Pattern to find: "HELLO" 🎯 Goal: Find where the pattern appears in the text! ❌ Simple approach: Compare 5 chars at every position → Worst case O(n×m) = many comparisons needed ✅ There's a faster way!
String Hashing converts strings into unique numbers (hash values). Polynomial Hash Formula: hash = (c[0]×p^(n-1) + c[1]×p^(n-2) + ... + c[n-1]) mod m Where c[i] is ASCII code, p is base (usually 31), m is a large prime. Rolling hash enables O(1) hash update when window slides, achieving O(n+m) for pattern matching!