Submission #1778495

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Source Code Expand

#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long int ll;

const ll INF = (ll)2e18;
const ll MOD = 1000000007LL;

ll S[100010];
ll dp[100010];
int main() {
    ll N, A, B; scanf("%lld%lld%lld", &N, &A, &B);
    if(A > B) swap(A, B);
    S[0] = S[1] = -INF;
    for(int i=0; i<N; i++) scanf("%lld", &S[i+2]);

    dp[1] = 1;
    int ptr = 1;
    for(int i=2; i<N+2; i++) {
        if(S[i] - S[i-2] < A) {
            printf("0\n");
            return 0;
        }
        // current: i
        // prev: i-1

        // 二つ目の山に入れる
        int lb = ptr - 1;
        int ub = upper_bound(S, S+N+2, S[i] - B) - S - 1;
        ll val = (lb >= ub ? 0 : dp[ub]);

        // 一つ目の山に入れる
        ll diff = S[i] - S[i-1];
        if(diff < A) {
            // dp[i-2] 以前の要素は全て 0 になる
            // 0 でない値が格納されているインデックスの下限は i-1 になり、
            // その値について、累積を解除
            ptr = i-1;
            dp[i-1] = (dp[i-1] - dp[i-2] + MOD) % MOD;
        }
        dp[i] = (dp[i-1] + val) % MOD;
    }

    printf("%lld\n", dp[N+1]);
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:12:50: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     ll N, A, B; scanf("%lld%lld%lld", &N, &A, &B);
                                                  ^
./Main.cpp:15:50: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     for(int i=0; i<N; i++) scanf("%lld", &S[i+2]);
                                                  ^

Judge Result