Create strings-differ-by-one-character.cpp

Author: kamyu104

C++/strings-differ-by-one-character.cpp

@@ -0,0 +1,39 @@
+// Time:  O(n * m)
+// Space: O(n)
+
+class Solution {
+public:
+    bool differByOne(vector<string>& dict) {
+        static const int MOD = 1e9 + 7;
+        static const int64_t P = 113;
+
+        vector<int> hashes(dict.size());
+        for (int i = 0; i < dict.size(); ++i) {
+            for (const auto& c : dict[i]) {
+                hashes[i] = (P * hashes[i] + (c - 'a')) % MOD;
+            }
+        }
+
+        int64_t base = 1;
+        for (int p = dict[0].length() - 1; p >= 0; --p) {
+            unordered_map<int, vector<int>> lookup;
+            for (int i = 0; i < dict.size(); ++i) {
+                int new_hash = ((hashes[i] - base * (dict[i][p] - 'a') % MOD) + MOD) % MOD;
+                if (lookup.count(new_hash)) {
+                    auto target = dict[i].substr(0, p);
+                    target += dict[i].substr(p + 1);
+                    for (const auto& j : lookup[new_hash]) {
+                        auto candidate = dict[j].substr(0, p);
+                        candidate += dict[j].substr(p + 1);
+                        if (candidate == target) {
+                            return true;
+                        }
+                    }
+                }
+                lookup[new_hash].emplace_back(i);
+            }
+            base = (P * base) % MOD;
+        }
+        return false;
+    }
+};