Create find-all-good-strings.cpp

Author: kamyu104

C++/find-all-good-strings.cpp

@@ -0,0 +1,73 @@
+// Time:  O(m * n)
+// Space: O(m)
+
+class Solution {
+public:
+    int findGoodStrings(int n, string s1, string s2, string evil) {
+        const auto& prefix = getPrefix(evil);
+        vector<vector<vector<vector<int>>>> dp(
+            2, vector<vector<vector<int>>>(
+                   2, vector<vector<int>>(
+                          2, vector<int>(evil.length()))));
+        dp[0][0][0][0] = 1;
+        for (int i = 0; i < n; ++i) {
+            dp[(i + 1) % 2] = vector<vector<vector<int>>>(
+                                  2, vector<vector<int>>(
+                                      2, vector<int>(evil.length())));
+            for (int j = 0; j < 2; ++j) {
+                for (int k = 0; k < 2; ++k) {
+                    const auto min_c = j ? 'a' : s1[i];
+                    const auto max_c = k ? 'z' : s2[i];
+                    for (int l = 0; l < evil.length(); ++l) {
+                        if (!dp[i % 2][j][k][l]) {
+                            continue;
+                        }
+                        for (char c = min_c; c <= max_c; ++c) {
+                            int m = l - 1;
+                            while (m != -1 && evil[m + 1] != c) {
+                                m = prefix[m];
+                            }
+                            if (evil[m + 1] == c) {
+                                ++m;
+                            }
+                            if (m + 1 == evil.length()) {
+                                continue;
+                            }
+                            add(&dp[(i + 1) % 2][j || c != s1[i]][k || c != s2[i]][m + 1], dp[i % 2][j][k][l]);
+                        }
+                    }
+                }
+            }
+        }
+        int result = 0;
+        for (int j = 0; j < 2; ++j) {
+            for (int k = 0; k < 2; ++k) {
+                for (int l = 0; l < evil.length(); ++l) {
+                    add(&result, dp[n % 2][j][k][l]);
+                }
+            }
+        }
+        return result;
+    }
+
+private:
+    vector<int> getPrefix(const string& pattern) {
+        vector<int> prefix(pattern.length(), -1);
+        int j = -1;
+        for (int i = 1; i < pattern.length(); ++i) {
+            while (j != -1 && pattern[j + 1] != pattern[i]) {
+                j = prefix[j];
+            }
+            if (pattern[j + 1] == pattern[i]) {
+                ++j;
+            }
+            prefix[i] = j;
+        }
+        return prefix;
+    }
+    
+    void add(int *x, int y) {
+        static const int MOD = 1e9 + 7;
+        *x = (*x + y) % MOD;
+    }
+};