Problem F: Frequent values

You are given a sequence of n integers a₁ , a₂ , ... , a_n in non-decreasing order. In addition to that, you are given several queries consisting of indices i and j (1 ≤ i ≤ j ≤ n). For each query, determine the most frequent value among the integers a_i , ... , a_j.

Input Specification

The input consists of several test cases. Each test case starts with a line containing two integers n and q (1 ≤ n, q ≤ 100000). The next line contains n integers a₁ , ... , a_n (-100000 ≤ a_i ≤ 100000, for each i ∈ {1, ..., n}) separated by spaces. You can assume that for each i ∈ {1, ..., n-1}: a_i ≤ a_i+1. The following q lines contain one query each, consisting of two integers i and j (1 ≤ i ≤ j ≤ n), which indicate the boundary indices for the query.

The last test case is followed by a line containing a single 0.

Output Specification

For each query, print one line with one integer: The number of occurrences of the most frequent value within the given range.

Sample Input

10 3
-1 -1 1 1 1 1 3 10 10 10
2 3
1 10
5 10
0

Sample Output

1
4
3

RMQ问题

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <string>
 7 #include <vector>
 8 #include <stack>
 9 #include <queue>
10 #include <set>
11 #include <map>
12 #include <list>
13 #include <iomanip>
14 #include <cstdlib>
15 #include <sstream>
16 using namespace std;
17 typedef long long LL;
18 const int INF=0x5fffffff;
19 const double EXP=1e-6;
20 const int MS=100005;
21
22 int dp[MS][20];
23 int a[MS],cnt[MS];
24 int num[MS],l[MS],r[MS];
25 int n,q;
26
27 void RMQ_init()
28 {
29     for(int i=0;i<n;i++)
30         dp[i][0]=cnt[i];
31     for(int j=1;(1<<j)<=n;j++)
32     {
33         for(int i=0;i+(1<<j)-1<n;i++)
34             dp[i][j]=max(dp[i][j-1],dp[i+(1<<(j-1))][j-1]);
35     }
36 }
37
38 int RMQ(int l,int r)
39 {
40     int k=0;
41     while(1<<(k+1)<=r-l+1)
42         k++;
43     return max(dp[l][k],dp[r-(1<<k)+1][k]);
44 }
45
46
47
48 int main()
49 {
50     while(scanf("%d%d",&n,&q)==2&&n)
51     {
52         for(int i=0;i<n;i++)
53             scanf("%d",&a[i]);
54         a[n]=a[n-1]+1;
55         int start=0;
56         int id=0;
57         for(int i=0;i<=n;i++)
58         {
59             if(i>0&&a[i]>a[i-1])
60             {
61                 for(int j=start;j<i;j++)
62                     r[j]=i-1;
63                 cnt[id]=i-start;
64                 id++;
65                 start=i;
66             }
67             l[i]=start;
68             num[i]=id;
69         }
70         n=id;
71         RMQ_init();
72         int x,y;
73         while(q--)
74         {
75             scanf("%d%d",&x,&y);
76             x--;
77             y--;
78             int ans=0;
79             if(num[x]==num[y])
80             {
81                 printf("%d\n",y-x+1);
82                 continue;
83             }
84             ans=max(r[x]-x+1,y-l[y]+1);
85             if(num[x]+1<num[y])
86                 ans=max(ans,RMQ(num[x]+1,num[y]-1));
87             printf("%d\n",ans);
88         }
89
90     }
91     return 0;
92 }