hdu 3530 区间和在一定范围内最长区间

http://acm.hust.edu.cn/vjudge/problem/11253

这题要找到区间和在[m,k]范围内的最长区间

用两个单调序列保存区间最大值和最小值。当最大值-最小值》k时更新head，如果最大值-最小值>=m更新答案

#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <cctype>
#include <vector>
#include <iterator>
#include <set>
#include <map>
#include <sstream>
using namespace std;

#define mem(a,b) memset(a,b,sizeof(a))
#define pf printf
#define sf scanf
#define spf sprintf
#define pb push_back
#define debug printf("!
")
#define MAXN 1000000+5
#define MAX(a,b) a>b?a:b
#define blank pf("
")
#define LL long long
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define pqueue priority_queue
#define INF 0x3f3f3f3f

#define ls (rt<<1)
#define rs (rt<<1|1)

int n,m,k;

int p1[MAXN],p2[MAXN],a[MAXN],ans;

void getL()
{
    int h1,h2,r1,r2,pre;
    h1=h2=pre=1;
    r1=r2=ans=0;
    for(int i=1;i<=n;i++)
    {
        while(h1<=r1 && a[i]<=a[p1[r1]]) r1--;
        p1[++r1] = i;
        while(h2<=r2 && a[i]>=a[p2[r2]]) r2--;
        p2[++r2] = i;
        while(h1<=r1 && h2<=r2 && a[p2[h2]] - a[p1[h1]] > k)
        {
            if(p1[h1]>p2[h2]) pre = p2[h2++]+1;
            else pre = p1[h1++]+1;
        }
        if(h1<=r1 && h2<=r2 && a[p2[h2]] - a[p1[h1]]>=m)
        {
            ans = max(ans,i-pre+1);
        }
    }
}

int main()
{
    int i,j,t,kase=1;
    while(~sf("%d%d%d",&n,&m,&k))
    {
        for(i=1;i<=n;i++) sf("%d",&a[i]);
        getL();
        pf("%d
",ans);
    }
    return 0;
}