数算！

dsa/ch4_string/dsa_0404_string_loop.cpp

@@ -0,0 +1,47 @@
+#include <iostream>
+#include <vector>
+
+std::ostream& operator<<(std::ostream& os, const std::vector<int>& vector) {
+    for (const auto elem : vector) {
+        os << elem << ' ';
+    }
+    return os;
+}
+
+std::vector<int> prefix_function(const std::string& s) {
+    std::vector<int> pi(s.size());
+    for (int i = 1; i < s.size(); i++) {
+        int j = pi[i - 1];
+        while (true) {
+            if (s[i] == s[j]) {
+                pi[i] = j + 1;
+                break;
+            }
+            if (j == 0) {
+                pi[i] = 0;
+                break;
+            }
+            j = pi[j - 1];
+        }
+    }
+    return pi;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string s;
+    while (std::cin >> s && s != ".") {
+        auto pi = prefix_function(s);
+        std::clog << pi << std::endl;
+        int period = static_cast<int>(s.size()) - pi.back();
+        if (s.size() % period != 0) {
+            std::cout << 1 << std::endl;
+        } else {
+            std::cout << s.size() / period << std::endl;
+        }
+    }
+
+    return 0;
+}