Naive implementation of LCS

lcs_naive.cpp

#include <iostream>
#include <string>

using namespace std;

int N, M;
string S, T;

int calc(int n, int m) {
  if (n == N || m == M)
    return 0;

  if (S[n] == T[m]) {
    return calc(n+1, m+1) + 1;
  } else {
    return max(calc(n+1, m), calc(n, m+1));
  }
}

void solve() {
  int res = calc(0, 0);
  cout << res << endl;
}

int main() {
  cout << "n: "; cin >> N;
  cout << "m: "; cin >> M;
  cout << "s: "; cin >> S;
  cout << "t: "; cin >> T;
  solve();
  return 0;
}