【CodeVS 3289】【NOIP 2013】花匠

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 100003;
int in() {
int k = 0, fh = 1; char c = getchar();
for(; c < '0' || c > '9'; c = getchar())
if (c == '-') fh = -1;
for(; c >= '0' && c <= '9'; c = getchar())
k = (k << 3) + (k << 1) + c - '0';
return k * fh;
}

int n, h
, H
, cnt, bit1
, bit2
;

void update1(int pos, int x) {
for(; pos; pos -= (pos & (-pos)))
bit1[pos] = max(bit1[pos], x);
}
int Max1(int pos) {
int ret = 0;
for(; pos < cnt; pos += (pos & (-pos)))
ret = max(ret, bit1[pos]);
return ret;
}

void update2(int pos, int x) {
for(; pos < cnt; pos += (pos & (-pos)))
bit2[pos] = max(bit2[pos], x);
}
int Max2(int pos) {
int ret = 0;
for(; pos; pos -= (pos & (-pos)))
ret = max(ret, bit2[pos]);
return ret;
}

int ans = 0, f;

int main() {
n = in(); cnt = n;
for(int i = 1; i <= n; ++i) {
h[i] = in();
H[i] = h[i];
}
sort(H + 1, H + n + 1);
cnt = unique(H + 1, H + cnt + 1) - H;
for(int i = 1; i <= n; ++i)
h[i] = lower_bound(H + 1, H + cnt, h[i]) - H;

update1(h[1], 1); update2(h[1], 1);
for(int i = 2; i <= n; ++i) {
f = Max1(h[i] + 1);
update2(h[i], f + 1);
ans = max(ans, f);
f = Max2(h[i] - 1);
update1(h[i], f + 1);
ans = max(ans, f);
}

printf("%d\n", ans + 1);
return 0;
}