开始计概A下半学期。

dsa/ch4_string/template_kmp_elegent.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <vector>
+
+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 (j > 0 && s[i] != s[j]) {
+            j = pi[j - 1];
+        }
+        if (s[i] == s[j]) { j++; }
+        pi[i] = j;
+    }
+    return pi;
+}
+
+std::vector<int> find_substring_pos(const std::string& target, const std::string& pattern) {
+    std::vector<int> matched_pos;
+    const std::vector<int> pattern_prefix_values = prefix_function(pattern);
+    int j = 0;
+    for (int i = 0; i < target.size(); i++) {
+        while (j > 0 && target[i] != pattern[j]) {
+            j = pattern_prefix_values[j - 1];
+        }
+        if (target[i] == pattern[j]) { j++; }
+        if (j == pattern.size()) {
+            matched_pos.push_back(i - static_cast<int>(pattern.size()) + 1);
+            j = pattern_prefix_values[j - 1];
+        }
+    }
+    return matched_pos;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string target, pattern;
+    std::cin >> target >> pattern;
+    for (const auto i : find_substring_pos(target, pattern)) {
+        std::cout << i << " ";
+    }
+    std::cout << std::endl;
+
+    return 0;
+}