【DP】 codeforces 487B Strip

单调队列优化DP。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 1000005
#define maxm 2000005
#define eps 1e-10
#define mod 1000000007
#define INF 0x3f3f3f3f
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
#define pii pair<int, int>
//#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
// head

deque<pii> mx, mi;
int dp[maxn];
int a[maxn];
int n, s, l;

void read(void)
{
	scanf("%d%d%d", &n, &s, &l);
	for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
}

void work(void)
{
	dp[0] = 0;
	for(int i = 1, p = 1; i <= n; i++) {
		while(!mx.empty() && mx.back().first <= a[i]) mx.pop_back();
		while(!mi.empty() && mi.back().first >= a[i]) mi.pop_back();
		mx.push_back(mp(a[i], i));
		mi.push_back(mp(a[i], i));
		while(p < i && (dp[p-1] == -1 || mx.front().first - mi.front().first > s)) {
			p++;
			while(mx.front().second < p) mx.pop_front();
			while(mi.front().second < p) mi.pop_front();
		}
		if(i - p + 1 < l || dp[p-1] == -1) dp[i] = -1;
		else dp[i] = dp[p-1] + 1;
	}
	printf("%d\n", dp[n]);
}

int main(void)
{
	read();
	work();

	return 0;
}