Add test for manacher_odd

Yurii A. · Yurii A. · commit 1df43b8312aa · 2024-11-14T16:05:08.000+02:00
diff --git a/src/string/manacher.md b/src/string/manacher.md
@@ -140,7 +140,7 @@ For calculating $d_{odd}[]$, we get the following code. Things to note:
  - The while loop denotes the trivial algorithm. We launch it irrespective of the value of $k$.
  - If the size of palindrome centered at $i$ is $x$, then $d_{odd}[i]$ stores $\frac{x+1}{2}$.
 
-```cpp
+```{.cpp file=manacher_odd}
 vector<int> manacher_odd(string s) {
     int n = s.size();
     s = "$" + s + "^";
diff --git a/test/test_manacher_odd.cpp b/test/test_manacher_odd.cpp
@@ -0,0 +1,74 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+#include "manacher_odd.h"
+
+string getRandomString(size_t n, uint32_t seed, char minLetter='a', char maxLetter='b') {
+    assert(minLetter <= maxLetter);
+    const size_t nLetters = static_cast<int>(maxLetter) - static_cast<int>(minLetter) + 1;
+    static std::uniform_int_distribution<size_t> distr(0, nLetters - 1);
+    std::mt19937 gen(seed);
+
+    string res;
+    res.reserve(n);
+
+    for (size_t i = 0; i < n; ++i)
+        res.push_back('a' + distr(gen));
+
+    return res;
+}
+
+bool testManacherOdd(const std::string &s) {
+    const auto n = s.size();
+    const auto d_odd = manacher_odd(s);
+
+    if (d_odd.size() != n)
+        return false;
+
+    const auto inRange = [&](size_t idx) {
+        return idx >= 0 && idx < n;
+    };
+
+    for (size_t i = 0; i < n; ++i) {
+        if (d_odd[i] < 0)
+            return false;
+        for (int d = 0; d < d_odd[i]; ++d) {
+            const auto idx1 = i - d;
+            const auto idx2 = i + d;
+
+            if (!inRange(idx1) || !inRange(idx2))
+                return false;
+            if (s[idx1] != s[idx2])
+                return false;
+        }
+
+        const auto idx1 = i - d_odd[i];
+        const auto idx2 = i + d_odd[i];
+        if (inRange(idx1) && inRange(idx2) && s[idx1] == s[idx2])
+            return false;
+    }
+
+    return true;
+}
+
+int main() {
+    vector<string> testCases;
+
+    testCases.push_back("");
+    for (size_t i = 1; i <= 25; ++i) {
+        auto s = string{};
+        s.resize(i, 'a');
+        testCases.push_back(move(s));
+    }
+    testCases.push_back("abba");
+    testCases.push_back("abccbaasd");
+    for (size_t n = 9; n <= 100; n += 10)
+        testCases.push_back(getRandomString(n, /* seed */ n, 'a', 'd'));
+    for (size_t n = 7; n <= 100; n += 10)
+        testCases.push_back(getRandomString(n, /* seed */ n));
+
+    for (const auto &s: testCases)
+        assert(testManacherOdd(s));
+
+    return 0;
+}
