## 紫书 防线 UVa1471

``````#include<cstdio>
#include<set>
#include<cassert>
using namespace std;

const int maxn = 200000 + 5;
int n, a[maxn], f[maxn], g[maxn];

struct Candidate {

int a, g;
Candidate(int a, int g):a(a),g(g) {

}
bool operator < (const Candidate& rhs) const {

return a < rhs.a;
}
};

set<Candidate> s;

int main() {

int T;
scanf("%d", &T);
while(T--) {

scanf("%d", &n);
for(int i = 0; i < n; i++)
scanf("%d", &a[i]);
if(n == 1) {

printf("1\n"); continue; }

// g[i] is the length of longest increasing continuous subsequence ending at i
g[0] = 1;
for(int i = 1; i < n; i++)
if(a[i-1] < a[i]) g[i] = g[i-1] + 1;
else g[i] = 1;

// f[i] is the length of longest increasing continuous subsequence starting from i
f[n-1] = 1;
for(int i = n-2; i >= 0; i--)
if(a[i] < a[i+1]) f[i] = f[i+1] + 1;
else f[i] = 1;

s.clear();
s.insert(Candidate(a[0], g[0]));
int ans = 1;
for(int i = 1; i < n; i++) {

Candidate c(a[i], g[i]);
set<Candidate>::iterator it = s.lower_bound(c); // first one that is >= c
bool keep = true;
if(it != s.begin()) {

Candidate last = *(--it); // (--it) points to the largest one that is < c
int len = f[i] + last.g;
ans = max(ans, len);
if(c.g <= last.g) keep = false;
}

if(keep) {

//s.erase(c); // if c.a is already present, the old g must be <= c.g
s.insert(c);
it = s.find(c); // this is a bit cumbersome and slow but it's clear
it++;
while(it != s.end() && it->a > c.a && it->g <= c.g) s.erase(it++);
}
}
printf("%d\n", ans);
}
return 0;
}

``````