#include <stdio.h>
#include <vector>
long long int solution(const std::vector<int> &position, const int n, const int l, const int r, const int top)
{
if (l == 1 && r == n)
return 1;
const auto high = n - top + 1;
const auto size = r - l + 1;
if (top <= size / 2)
return 0;
auto lsize = l - 1;
auto rsize = n - r;
if (position[high - 1] < l)
lsize = l - position[high - 1] - 1;
if (r < position[high - 1])
rsize = position[high - 1] - r - 1;
const auto msize = std::max(0, top - (size - top) - 1);
lsize = std::min(lsize, msize);
rsize = std::min(rsize, msize);
long long int sum{0};
const auto min = std::min(lsize, rsize);
const auto max = std::max(lsize, rsize);
{
const auto index = std::min(msize, min - 1) + 1;
sum += (1 + index) * (index) / 2;
}
if (min <= msize)
{
const auto count = std::min(msize - min + 1, max - min + 1);
sum += count * (min + 1);
}
if (max < msize)
{
const auto a = min;
const auto b = std::max(1, min + 1 - (msize - max));
sum += (a + b) * (a - b + 1) / 2;
}
return sum;
}
long long int solution(const std::vector<int> &position, const int n)
{
long long int permutation = 1;
int top = 1;
int l = position[n];
int r = position[n];
for (int i = n - 1; i >= 1; --i)
{
if (position[i] < l || r < position[i])
{
const auto p = position[i];
l = std::min(l, p);
r = std::max(r, p);
for (int j = i; j >= 1; --j)
{
if (l <= position[j] && position[j] <= r)
top++;
else
break;
}
permutation += solution(position, n, l, r, top);
}
}
return permutation;
}
int main()
{
int n, a;
std::vector<int> position;
scanf("%d", &n);
position.resize(n + 1);
for (int i = 1; i <= n; ++i)
{
scanf("%d", &a);
position[a] = i;
}
printf("%d %lld\n", 2 * n + 1, solution(position, n));
return 0;
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 | #include <stdio.h> #include <vector> long long int solution(const std::vector<int> &position, const int n, const int l, const int r, const int top) { if (l == 1 && r == n) return 1; const auto high = n - top + 1; const auto size = r - l + 1; if (top <= size / 2) return 0; auto lsize = l - 1; auto rsize = n - r; if (position[high - 1] < l) lsize = l - position[high - 1] - 1; if (r < position[high - 1]) rsize = position[high - 1] - r - 1; const auto msize = std::max(0, top - (size - top) - 1); lsize = std::min(lsize, msize); rsize = std::min(rsize, msize); long long int sum{0}; const auto min = std::min(lsize, rsize); const auto max = std::max(lsize, rsize); { const auto index = std::min(msize, min - 1) + 1; sum += (1 + index) * (index) / 2; } if (min <= msize) { const auto count = std::min(msize - min + 1, max - min + 1); sum += count * (min + 1); } if (max < msize) { const auto a = min; const auto b = std::max(1, min + 1 - (msize - max)); sum += (a + b) * (a - b + 1) / 2; } return sum; } long long int solution(const std::vector<int> &position, const int n) { long long int permutation = 1; int top = 1; int l = position[n]; int r = position[n]; for (int i = n - 1; i >= 1; --i) { if (position[i] < l || r < position[i]) { const auto p = position[i]; l = std::min(l, p); r = std::max(r, p); for (int j = i; j >= 1; --j) { if (l <= position[j] && position[j] <= r) top++; else break; } permutation += solution(position, n, l, r, top); } } return permutation; } int main() { int n, a; std::vector<int> position; scanf("%d", &n); position.resize(n + 1); for (int i = 1; i <= n; ++i) { scanf("%d", &a); position[a] = i; } printf("%d %lld\n", 2 * n + 1, solution(position, n)); return 0; } |
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