Submission #1075953

---

Source Code Expand

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif

#include <bits/stdc++.h>

using namespace std;

#define mp make_pair
#define pb push_back
#define sz(s) ((int) ((s).size()))

#ifdef DEBUG
#define eprintf(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#else
#define eprintf(...) ;
#endif

#ifdef _WIN32
#define LLD "%I64d"
#else
#define LLD "%lld"
#endif

typedef long long ll;
typedef long double ld;

const int inf = (int) 1e9 + 100;
const ld eps = 1e-11;
const ld pi = acos(-1.0L);

mt19937 mrand(random_device{} ());
int rnd(int x) {
  return mrand() % x;
}

const int mod = 1e9 + 7;

void add(int & a, int b) {
  if ((a += b) >= mod) {
    a -= mod;
  }
}

int mult(int a, int b) {
  return (ll) a * b % mod;
}

void precalc() {
}

int n, m, k;

bool read() {
  if (scanf("%d%d%d", &n, &m, &k) < 3) {
    return false;
  }
  return true;
}

const int maxn = 2100;

int dp[maxn], ndp[maxn];

void solve() {
  for (int i = 0; i < k; i++) {
    dp[i] = 1;
  }
  int res = 0;
  for (int i = 1; ; i++) {
    int all = i * (k - 1) + 1;
    if (all > n + m) {
      break;
    }
    for (int j = 1; j <= m; j++) {
      if ((m - j) % (k - 1) == 0 && (all - j) <= n) {
        add(res, dp[j]);
      }
    }
    memset(ndp, 0, sizeof(ndp));
    for (int j = 1; j <= m; j++) {
      for (int r = j; r < j + k && r <= m; r++) {
        add(ndp[r], dp[j]);
      }
    }
    swap(ndp, dp);
  }
  printf("%d\n", res);
}

int main() {
  precalc();
#ifdef DEBUG
  assert(freopen("text.in", "r", stdin));
  assert(freopen("text.out", "w", stdout));
#endif

  while (read()) {
    solve();
#ifdef DEBUG
    eprintf("Time: %.18f\n", (double) clock() / CLOCKS_PER_SEC);
#endif
  }
  return 0;
}

Submission Info

Judge Result