Problem p01484 (C++) — buggy submission, verdict: Memory Limit Exceeded

#include <algorithm>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <sstream>
#include <vector>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define fr(i, c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); i++)
#define pb push_back
#define mp make_pair
#define all(c) c.begin(), c.end()
#define dbg(x) cerr << #x << " = " << (x) << endl

typedef vector<int> vi;
typedef pair<int, int> pi;
typedef long long ll;
const int inf = (int)1e9;
const double EPS = 1e-9, INF = 1e12;

// Larsson-Sadakane's Suffix array Construction: O(n (log n)^2)
struct SAComp {
  const int h, *g;
  SAComp(int h, int *g) : h(h), g(g) {}
  bool operator()(int a, int b) {
    return a == b ? false : g[a] != g[b] ? g[a] < g[b] : g[a + h] < g[b + h];
  }
};
int *buildSA(char *t, int n) {
  int g[n + 1], b[n + 1], *v = new int[n + 1];
  rep(i, n + 1) v[i] = i, g[i] = t[i];
  b[0] = 0;
  b[n] = 0;

  sort(v, v + n + 1, SAComp(0, g));
  for (int h = 1; b[n] != n; h *= 2) {
    SAComp comp(h, g);
    sort(v, v + n + 1, comp);
    rep(i, n) b[i + 1] = b[i] + comp(v[i], v[i + 1]);
    rep(i, n + 1) g[v[i]] = b[i];
  }
  return v;
}
// Naive matching O(m log n)
int find(char *t, int n, char *p, int m, int *sa) {
  int a = 0, b = n;
  while (a < b) {
    int c = (a + b) / 2;
    if (strncmp(t + sa[c], p, m) < 0)
      a = c + 1;
    else
      b = c;
  }
  return strncmp(t + sa[a], p, m) == 0 ? sa[a] : -1;
}
int n, m, k;
string s;
char *sc, t[500];
int *sa, len;

ll ck() {
  ll res = 0;
  for (int l = 0, r = 0; l < m; l++) {
    while (r < l)
      r++;
    while (r < m) {
      char tmp = t[r + 1];
      t[r + 1] = 0;
      bool res = find(sc, len, t + l, r - l + 1, sa) >= 0;
      t[r + 1] = tmp;
      if (!res)
        break;
      r++;
    }
    res += r - l;
  }
  return res;
}

const string rec(int l, int r) {
  if (l >= r)
    return "";

  if (isdigit(s[l])) {
    int i, x = 0, d = 0;
    for (; l < r && isdigit(s[l]); l++) {
      x *= 10;
      x += s[l] - '0';
      x = min(x, 400);
    }
    for (i = l; i < r; i++) {
      if (s[i] == '(')
        d++;
      if (s[i] == ')')
        d--;
      if (d == 0)
        break;
    }
    string res = "", tmp = rec(l + 1, i);
    if (x == 1)
      return tmp;

    rep(i, x - 1) {
      res += tmp;
      if (res.size() > 400)
        break;
    }
    const string str = res + tmp;
    if (str.size() <= 800)
      return str + rec(i + 1, r);
    const string head400 = str.substr(0, min((int)str.size(), 400));
    const string tail400 = str.substr(max(0, (int)str.size() - 400));

    const string tail = tmp.substr(max(0, (int)tmp.size() - 400));
    const string head = tmp.substr(0, min(400, (int)tmp.size()));

    return head400 + "@" + tail + res + head + "@" + tail400 + rec(i + 1, r);
  }
  return s[l] + rec(l + 1, r);
}
int main() {
  cin >> n >> m >> k;
  cin >> s;
  s = rec(0, n);
  len = s.size();
  sc = (char *)malloc(len + 1);
  sprintf(sc, "%s", s.c_str());
  s.clear();
  sa = buildSA(sc, len);

  int ansi = 0;
  ll ans = 0;
  rep(i, k) {
    cin >> t;
    ll tmp = ck();
    if (tmp > ans)
      ans = tmp, ansi = i;
  }
  cout << ansi + 1 << " " << ans << endl;

  return 0;
}

Error: MLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <sstream>
#include <vector>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define fr(i, c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); i++)
#define pb push_back
#define mp make_pair
#define all(c) c.begin(), c.end()
#define dbg(x) cerr << #x << " = " << (x) << endl

typedef vector<int> vi;
typedef pair<int, int> pi;
typedef long long ll;
const int inf = (int)1e9;
const double EPS = 1e-9, INF = 1e12;

// Larsson-Sadakane's Suffix array Construction: O(n (log n)^2)
struct SAComp {
  const int h, *g;
  SAComp(int h, int *g) : h(h), g(g) {}
  bool operator()(int a, int b) {
    return a == b ? false : g[a] != g[b] ? g[a] < g[b] : g[a + h] < g[b + h];
  }
};
int *buildSA(char *t, int n) {
  int g[n + 1], b[n + 1], *v = new int[n + 1];
  rep(i, n + 1) v[i] = i, g[i] = t[i];
  b[0] = 0;
  b[n] = 0;

  sort(v, v + n + 1, SAComp(0, g));
  for (int h = 1; b[n] != n; h *= 2) {
    SAComp comp(h, g);
    sort(v, v + n + 1, comp);
    rep(i, n) b[i + 1] = b[i] + comp(v[i], v[i + 1]);
    rep(i, n + 1) g[v[i]] = b[i];
  }
  return v;
}
// Naive matching O(m log n)
int find(char *t, int n, char *p, int m, int *sa) {
  int a = 0, b = n;
  while (a < b) {
    int c = (a + b) / 2;
    if (strncmp(t + sa[c], p, m) < 0)
      a = c + 1;
    else
      b = c;
  }
  return strncmp(t + sa[a], p, m) == 0 ? sa[a] : -1;
}
int n, m, k;
string s;
char *sc, t[500];
int *sa, len;

ll ck() {
  ll res = 0;
  for (int l = 0, r = 0; l < m; l++) {
    while (r < l)
      r++;
    while (r < m) {
      char tmp = t[r + 1];
      t[r + 1] = 0;
      bool res = find(sc, len, t + l, r - l + 1, sa) >= 0;
      t[r + 1] = tmp;
      if (!res)
        break;
      r++;
    }
    res += r - l;
  }
  return res;
}

const string rec(int l, int r) {
  if (l >= r)
    return "";

  if (isdigit(s[l])) {
    int i, x = 0, d = 0;
    for (; l < r && isdigit(s[l]); l++) {
      x *= 10;
      x += s[l] - '0';
      x = min(x, 400);
    }
    for (i = l; i < r; i++) {
      if (s[i] == '(')
        d++;
      if (s[i] == ')')
        d--;
      if (d == 0)
        break;
    }
    string res = "", tmp = rec(l + 1, i);
    if (x == 1)
      return tmp;

    rep(i, x - 1) {
      res += tmp;
      if (res.size() > 400)
        break;
    }
    const string str = res + tmp;
    if (str.size() <= 800)
      return str + rec(i + 1, r);
    const string head400 = str.substr(0, min((int)str.size(), 400));
    const string tail400 = str.substr(max(0, (int)str.size() - 400));

    const string tail = tmp.substr(max(0, (int)tmp.size() - 400));
    const string head = tmp.substr(0, max(0, (int)tmp.size()));

    return head400 + "@" + tail + res + head + "@" + tail400 + rec(i + 1, r);
  }
  return s[l] + rec(l + 1, r);
}
int main() {
  cin >> n >> m >> k;
  cin >> s;
  s = rec(0, n);
  len = s.size();
  sc = (char *)malloc(len + 1);
  sprintf(sc, "%s", s.c_str());
  s.clear();
  sa = buildSA(sc, len);

  int ansi = 0;
  ll ans = 0;
  rep(i, k) {
    cin >> t;
    ll tmp = ck();
    if (tmp > ans)
      ans = tmp, ansi = i;
  }
  cout << ansi + 1 << " " << ans << endl;

  return 0;
}