Create words-within-two-edits-of-dictionary.cpp

Author: kamyu104

C++/words-within-two-edits-of-dictionary.cpp

@@ -0,0 +1,107 @@
+// Time:  O(25 * l * (n + q))
+// Space: O(25 * l * n)
+
+// hash
+class Solution {
+public:
+    vector<string> twoEditWords(vector<string>& queries, vector<string>& dictionary) {
+        static const uint64_t MOD = (1ull << 64) - 59;  // largest 64-bit prime
+        static const uint64_t BASE = 113;
+        vector<uint64_t> POW = {1};
+        const auto& add = [](uint64_t a, uint64_t b) {
+            if (MOD - a <= b) {
+                b -= MOD;  // relied on unsigned integer overflow in order to give the expected results
+            }
+            return a + b;
+        };
+        const auto& sub = [&](uint64_t a, uint64_t b) {
+            return add(a, MOD - b);
+        };
+        const auto& mult = [&](uint64_t a, uint64_t b)  { 
+            uint64_t result = 0;
+            if (a < b) {
+                swap(a, b);
+            }
+            while (b > 0)  { 
+                if (b % 2 == 1) {
+                    result = add(result, a);
+                }
+                a = add(a, a);
+                b /= 2; 
+            } 
+            return result;
+        };
+        const auto& pow = [&](int i) {
+            while (!(i < size(POW))) {
+                POW.emplace_back(mult(POW.back(), BASE));
+            }
+            return POW[i];
+        };
+    
+        unordered_set<uint64_t> lookup;
+        for (const auto& w : dictionary) {
+            uint64_t h = 0;
+            for (int i = 0; i < size(w); ++i) {
+                h = add(h, mult(sub(w[i], 'a'), pow(i)));
+            }
+            for (int i = 0; i < size(w); ++i) {
+                for (char x = 'a'; x <= 'z'; ++x) {
+                    if (x == w[i]) {
+                        continue;
+                    }
+                    lookup.emplace(add(h, mult(sub(x, w[i]), pow(i))));
+                }
+            }
+        }
+        vector<string> result;
+        for (const auto& w : queries) {
+            uint64_t h = 0;
+            for (int i = 0; i < size(w); ++i) {
+                h = add(h, mult(sub(w[i], 'a'), pow(i)));
+            }
+            for (int i = 0; i < size(w); ++i) {
+                char x = 'a';
+                for (; x <= 'z'; ++x) {
+                    if (x == w[i]) {
+                        continue;
+                    }
+                    if (lookup.count(add(h, mult(sub(x, w[i]), pow(i))))) {
+                        break;
+                    }
+                }
+                if (x <= 'z') {
+                    result.emplace_back(w);
+                    break;
+                }
+            }
+        }
+        return result;
+    }
+};
+
+// Time:  O(q * n * l)
+// Space: O(1)
+// brute force
+class Solution2 {
+public:
+    vector<string> twoEditWords(vector<string>& queries, vector<string>& dictionary) {
+        const auto& check = [&](const auto& w1, const auto& w2) {
+            int cnt = 0;
+            for (int i = 0; i < size(w1); ++i) {
+                cnt += static_cast<int>(w1[i] != w2[i]);
+            }
+            return cnt <= 2;
+        };
+        
+        vector<string> result;
+        for (const auto& q : queries) {
+            for (const auto& d : dictionary) {
+                if (check(q, d)) {
+                    result.emplace_back(q);
+                    break;
+                }
+            }
+        }
+        return result;
+    }
+};