多校第一场 hdu 5289 Assignment(rmq+二分)

题目链接：

点击打开链接

题目大意：

给出一个序列，问能找出多少个连续区间，区间内最大最小数的差小于k

题目分析：

直接rmq求取，区间最大最小值，枚举每个起点，二分终点，然后对于i点能够满足条件的最远区间到终点，所以贡献r-l+1，求取和就是最后结果

代码如下：

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#define MAX 100007

using namespace std;

typedef long long LL;

int dp[MAX][20];
int dp2[MAX][20];
int a[MAX];
int n,k;

void init ()
{
    for ( int i = 0 ; i < n ; i++ )
        dp[i][0] = a[i],dp2[i][0] = a[i];
    for ( int j = 1; (1<<j) <= n ; j++ )
        for ( int i = 0 ; i + (1<<j)-1 < n ; i++ )
        {
            dp[i][j] = max ( dp[i][j-1] , dp[i+(1<<(j-1))][j-1] );
            dp2[i][j] = min ( dp2[i][j-1] , dp2[i+(1<<(j-1))][j-1] );
        }
}

int big ( int l , int r )
{
    int k = (int)((log(r-l+1)*1.0)/(log(2.0)));
    return max ( dp[l][k] , dp[r-(1<<k)+1][k] );
}

int small ( int l , int r )
{
    int k = (int)((log(r-l+1)*1.0)/(log(2.0)));
    return min ( dp2[l][k] , dp2[r-(1<<k)+1][k] );
}

bool check ( int x , int mid , int k )
{
    return big( x , mid )-small ( x , mid ) < k;
}

int search ( int x, int k )
{
    int l = x , r = n-1 , mid;
    while ( l != r )
    {
        mid = (l+r+1)>>1;
        if ( check ( x , mid , k )) l = mid;
        else r = mid-1;
    }
    return l;
}

int t;

int main ( )
{
    scanf ( "%d" , &t );
    while ( t-- )
    {
        scanf ( "%d%d" , &n , &k );
        for ( int i = 0 ; i < n ; i++ )
            scanf ( "%d" , &a[i] );
        init();
        int i = 0;
        LL ans = 0;
        while ( i < n )
        {
            //int x = search ( i , k );
            int l = i , r = n-1 , mid;
            while ( l != r )
            {
                mid = (l+r+1)>>1;
                if ( check ( i , mid , k )) l = mid;
                else r = mid-1;
            }
            ans += l-i+1;
            i++;
        }
        printf ( "%I64d\n" , ans );
    }
}