#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> pi;
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) debug(x) debug(y);
#define repn(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(i, a) for(int i = 0; i < (int)(a); i++)
#define all(v) v.begin(), v.end()
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define sq(x) ((x) * (x))
const int MOD = 1e6 + 7;
template<class T> T gcd(T a, T b){ return ((b == 0) ? a : gcd(b, a % b)); }
int dp[1005][1005][2];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
//freopen("input.in", "r", stdin);
//freopen("output.out", "w", stdout);
int n;
cin >> n;
vi a(n);
rep(i, n) cin >> a[i];
rep(i, 1005) rep(j, 1005) rep(k, 2) dp[i][j][k] = 0;
dp[0][1][1] = 1;
dp[0][1][0] = 0;
repn(i, 1, n){
repn(k, 1, i + 2){
repn(j, 1, i + 1) if((k - 1) <= j){
if(k < a[i]){
//we can make a 1 into a 0
dp[i][max(j, k)][0] = (dp[i][max(j, k)][0] + dp[i - 1][j][1]) % MOD;
}
//update the 0 guy
dp[i][max(j, k)][0] = (dp[i][max(j, k)][0] + dp[i - 1][j][0]) % MOD;
if(k == a[i]) dp[i][max(j, k)][1] = (dp[i][max(j, k)][1] + dp[i - 1][j][1]) % MOD;
}
}
}
ll ans = 0;
repn(i, 1, n + 1) ans = (ans + dp[n - 1][i][0] + dp[n - 1][i][1]) % MOD;
cout << ans << endl;
return 0;
}
/*
Things to look out for:
- Integer overflows
- Array bounds
- Special cases
Be careful!
*/
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
9 ms |
8184 KB |
Output is correct |
2 |
Correct |
9 ms |
8312 KB |
Output is correct |
3 |
Correct |
9 ms |
8312 KB |
Output is correct |
4 |
Correct |
10 ms |
8184 KB |
Output is correct |
5 |
Correct |
9 ms |
8188 KB |
Output is correct |
6 |
Correct |
9 ms |
8312 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
9 ms |
8440 KB |
Output is correct |
2 |
Correct |
9 ms |
8184 KB |
Output is correct |
3 |
Correct |
9 ms |
8312 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
9 ms |
8312 KB |
Output is correct |
2 |
Correct |
9 ms |
8188 KB |
Output is correct |
3 |
Correct |
9 ms |
8184 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
10 ms |
8184 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
10 ms |
8184 KB |
Output is correct |
2 |
Correct |
10 ms |
8312 KB |
Output is correct |
3 |
Correct |
10 ms |
8312 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
79 ms |
8184 KB |
Output is correct |
2 |
Correct |
78 ms |
8184 KB |
Output is correct |
3 |
Correct |
112 ms |
8184 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
545 ms |
8324 KB |
Output is correct |
2 |
Correct |
544 ms |
8184 KB |
Output is correct |
3 |
Correct |
808 ms |
8324 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
824 ms |
16760 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
568 ms |
16656 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
554 ms |
16760 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
2 |
Halted |
0 ms |
0 KB |
- |