Submission #2553892

---

Source Code Expand

#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <climits>
#include <ctime>
#include <cassert>
using namespace std;

#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define repq(i,a,n) for(int (i)=(a); (i)<=(n); (i)++)
#define repr(i,a,n) for(int (i)=(a); (i)>=(n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a,b) (abs((a) - (b)) < EPS)
#define EQV(a,b) ( EQ((a).X, (b).X) && EQ((a).Y, (b).Y) )
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};
int const MOD = 1000000007;

int x[100010];
int N, L;
signed main() {
    cin >> N >> L;
    for(int i=0; i<N; i++) {
        cin >> x[i];
    }

    int left = x[0], last = 0, ok = true;
    for(int i=1; i<N; i++) {
        int pos = x[i], diff = x[i] - x[i-1];
        if(diff == L) ok = false;
        if(diff <  L) {
            if(pos - left > L) ok = false;
        }
        if(diff >  L) {
            int jump = max(last, x[i-1] - L);
            // printf("jump = %lld, pos = %lld, L = %lld\n", jump, pos, L);
            if(pos - 2*L <= jump) ok = false;

            last = jump + 2*L;
            left = pos;
        }

        if(!ok) break;
    }
    cout << (ok ? "YES" : "NO") << endl;
    return 0;
}

Submission Info

Judge Result