Ukkonen dp

libpz/fuzzy/ukkonen.cpp

@@ -0,0 +1,39 @@
+// Ukkonen Cutoff DP
+#include <iostream>
+#include <vector>
+#include <string>
+#include <algorithm>
+
+using namespace std;
+
+bool edit_within_k(const string& s, const string& t, int k) {
+    if (k < 0) return false;
+    int m = s.size();
+    int n = t.size();
+    if(abs(m-n) > k) return false;
+    int INF= k + 1;
+    vector<int> prev(2*k + 3, INF);
+    vector<int> curr(2*k + 3, INF);
+
+    for(int j = 0; j <= min(n, k); j++) {
+        int d=j;
+        prev[d+k+1] = j;
+    }
+    for(int i= 1; i <= m; i++) {
+        curr[0] = i;
+        int left = max(1, i-k);
+        int right = min(n, i+k);
+        for (int j=left; j<= right; j++) {
+            int d = j-i;
+            int idx = d+k+1;
+            int cost = (s[i-1] == t[j-1]) ? 0 : 1;
+            curr[idx] = min({
+                prev[idx+1] + 1,
+                curr[idx-1] + 1,
+                prev[idx] + cost
+            });
+        }
+        swap(prev, curr);
+    }
+    return prev[n-m+k+1] <= k;
+}

libpz/include/ukkonen.hpp

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+#ifndef UKKONEN_HPP
+#define UKKONEN_HPP
+#include <string>
+#include <vector>
+#include <algorithm>
+
+class Ukkonen {
+public:
+    explicit Ukkonen(int k);
+    bool edit_within_k(const std::string& s, const std::string& t);
+
+private:
+    int k_;
+};
+#endif