z algorithm

Author: KHvic

Z-Algorithm/z.cpp

@@ -0,0 +1,23 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// z_function is the number of characters ahead that is also the prefix starting from index i
+vector<int> z_function(string s) {
+    int n = s.length();
+    vector<int> z(n);
+    for (int i = 1, l = 0, r = 0; i < n; ++i) {
+        if (i <= r)
+            z[i] = min (r - i + 1, z[i - l]);
+        while (i + z[i] < n && s[z[i]] == s[i + z[i]])
+            ++z[i];
+        if (i + z[i] - 1 > r)
+            l = i, r = i + z[i] - 1;
+    }
+    return z;
+}
+
+int main(){
+    string s;
+    cin >> s;
+    for(auto z : z_function(s)) cout << z << " ";
+}