Submission #2414068

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

int N, A, B;
#define MAX_N 100000
long long S[MAX_N];
int FA[MAX_N], FB[MAX_N];
#define MOD 1000000007
long long X[MAX_N], Y[MAX_N];

void solve(int i, int a, int fb[MAX_N],
  long long x[MAX_N], long long y[MAX_N]) {
  int j = upper_bound(S, S + N, S[i] - a) - S - 1;
  if(j < 0) x[i] = fb[i - 1] - fb[0] == i - 1;
  else if(j == i - 1) x[i] = (x[i - 1] + y[i - 1]) % MOD;
  else {
    if(fb[i - 1] - fb[j + 1] == (i - 1) - (j + 1)) {
      x[i] = y[j + 1];
    } else {
      x[i] = 0;
    }
  }
}
int main() {
  cin >> N >> A >> B;
  for(int i = 0; i < N; ++i) cin >> S[i];
  FA[0] = FB[0] = 0;
  for(int i = 1; i < N; ++i) {
    FA[i] = FA[i - 1] + (S[i] - S[i - 1] >= A);
    FB[i] = FB[i - 1] + (S[i] - S[i - 1] >= B);
  }
  X[0] = Y[0] = 1;
  for(int i = 1; i < N; ++i) {
    solve(i, A, FB, X, Y);
    solve(i, B, FA, Y, X);
  }
  cout << (X[N - 1] + Y[N - 1]) % MOD << endl;
  return 0;
}

Submission Info

Judge Result