hdu 4604 Deque（LIS）

解题思路

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 100005;

struct Stack {
int n, s[maxn];
void init () { n = 0; }
int find (int x) { return upper_bound(s, s + n, x) - s; }
void modify(int pos, int val) { s[pos] = val; n = max(n, pos+1); }
}in, de;

int N, A[maxn];

int solve () {
in.init();
de.init();
int ret = 0;
for (int i = N; i; i--) {
int l = in.find(A[i]);
in.modify(l, A[i]);
int r = de.find(-(A[i]+1));
int tmp = de.find(-A[i]);
de.modify(tmp, -A[i]);
ret = max(ret, l + r);
}
return ret + 1;
}

int main () {
int cas;
scanf("%d", &cas);
while (cas--) {
scanf("%d", &N);
for (int i = 1; i <= N; i++) scanf("%d", &A[i]);
printf("%d\n", solve());
}
return 0;
}