11235 - Frequent values

《算法竞赛入门经典-训练指南》P198
记录一下区间的左右边界就可以了
#include <iostream>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <set>
#include <vector>
#include <cstring>
#include <algorithm>

#define INF 0x7fffffff
#define N 100010
#define M 1000010
#define LL long long
#define mod 95041567

using namespace std;

int arr
;
int num
[3];
int dp
[20];

void RMQ_init(int len){
for(int j = 1; (1 << j) <= len; ++ j)
for(int i = 1; i + (1 << j) - 1 < len; ++ i)
dp[i][j] = max(dp[i][j - 1], dp[i + (1 << (j - 1))][j - 1]);
}

int RMQ(int L, int R){
if(R < L) return 0;
else if(R == L) return dp[R][0];
int k = 0;
while((1 << (k + 1)) <= R - L + 1) ++ k;
return max(dp[L][k], dp[R - (1 << k) + 1][k]);
}

int main()
{
int n, q;
// freopen("in.txt","r",stdin);
while(scanf("%d", &n) != EOF){
if(! n) break;
scanf("%d", &q);
for(int i = 0; i < n; ++ i) scanf("%d", &arr[i]);
for(int i = 0; i <= n + 2; ++ i)
for(int j = 0; j <= 20; ++ j)
dp[i][j] = 0;
arr
= INF;
int p = 0;
int len = 0;
for(int i = 1; i <= n; ++ i)
if(arr[i] != arr[i - 1]){
for(int j = p; j <= i - 1; ++ j){
num[j][0] = i - 1;
num[j][1] = p;
num[j][2] = len;
}
dp[len ++][0] = i - p;
p = i;
}
RMQ_init(len);
int L, R;
for(int i = 0; i < q; ++ i){
scanf("%d %d", &L, &R);
if(arr[L - 1] == arr[R - 1]){
printf("%d\n", R - L + 1);
continue;
}
//printf("%s\n", "++");
p = num[L - 1][0] - (L - 1) + 1;
p = max(p, R - num[R - 1][1]);
p = max(p, RMQ(num[L - 1][2] + 1, num[R - 1][2] - 1));
printf("%d\n", p);
}
}
return 0;
}