Function z_function

Strings/Z Algorithm.cpp:8–20

An element Z[i] of Z array stores length of the longest substring starting from str[i] which is also a prefix of str[0..n-1]. The first entry of Z array is meaning less as complete string is always prefix of itself. Here Z[0]=0.

// The first entry of Z array is meaning less as complete string is always prefix of itself.
// Here Z[0]=0.
vector<int> z_function(string s) {
  int n = (int) 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;
}
int32_t main() {
  string s;
  cin >> s;