[HDOJ1806]Frequent values(RMQ,ST)

题目链接:http://acm.split.hdu.edu.cn/showproblem.php?pid=1806

题意:给1~n个单调不递减的数,求q次区间出现次数最多的那个数的次数。

由于单调不递减,是有一个顺序的。则可以考虑记录一个b(i)=第i个数字在前i个里出现了i次,一定是连续的。这样把它丢进st表里,query(l,r)表示的是区间l,r内出现最多的那个数的次数。但是有个问题,那就是最左端有可能不是从1开始的,则要先处理最左端,找到最左的第一个1的位置p,然后用p-l则就是那个数字出现的次数。

  1 /*
  2 ━━━━━┒ギリギリ♂ eye!
  3 ┓┏┓┏┓┃キリキリ♂ mind!
  4 ┛┗┛┗┛┃\○/
  5 ┓┏┓┏┓┃ /
  6 ┛┗┛┗┛┃ノ)
  7 ┓┏┓┏┓┃
  8 ┛┗┛┗┛┃
  9 ┓┏┓┏┓┃
 10 ┛┗┛┗┛┃
 11 ┓┏┓┏┓┃
 12 ┛┗┛┗┛┃
 13 ┓┏┓┏┓┃
 14 ┃┃┃┃┃┃
 15 ┻┻┻┻┻┻
 16 */
 17 #include <algorithm>
 18 #include <iostream>
 19 #include <iomanip>
 20 #include <cstring>
 21 #include <climits>
 22 #include <complex>
 23 #include <fstream>
 24 #include <cassert>
 25 #include <cstdio>
 26 #include <bitset>
 27 #include <vector>
 28 #include <deque>
 29 #include <queue>
 30 #include <stack>
 31 #include <ctime>
 32 #include <set>
 33 #include <map>
 34 #include <cmath>
 35 using namespace std;
 36 #define fr first
 37 #define sc second
 38 #define cl clear
 39 #define BUG puts("here!!!")
 40 #define W(a) while(a--)
 41 #define pb(a) push_back(a)
 42 #define Rint(a) scanf("%d", &(a))
 43 #define Rll(a) scanf("%lld", &a)
 44 #define Rs(a) scanf("%s", a)
 45 #define Cin(a) cin >> a
 46 #define FRead() freopen("in", "r", stdin)
 47 #define FWrite() freopen("out", "w", stdout)
 48 #define Rep(i, len) for(int i = 0; i < (len); i++)
 49 #define For(i, a, len) for(int i = (a); i < (len); i++)
 50 #define Cls(a) memset((a), 0, sizeof(a))
 51 #define Clr(a, x) memset((a), (x), sizeof(a))
 52 #define Full(a) memset((a), 0x7f, sizeof(a))
 53 #define lrt rt << 1
 54 #define rrt rt << 1 | 1
 55 #define pi 3.14159265359
 56 #define RT return
 57 #define lowbit(x) x & (-x)
 58 #define onenum(x) __builtin_popcount(x)
 59 typedef long long LL;
 60 typedef long double LD;
 61 typedef unsigned long long Uint;
 62 typedef pair<int, int> pii;
 63 typedef pair<LL, LL> pLL;
 64 typedef pair<string, LL> psi;
 65 typedef map<string, LL> msi;
 66 typedef vector<LL> vi;
 67 typedef vector<LL> vl;
 68 typedef vector<vl> vvl;
 69 typedef vector<bool> vb;
 70 
 71 const int maxn = 100100;
 72 int n, q;
 73 int a[maxn];
 74 int b[maxn];
 75 int dp[maxn][20];
 76 
 77 void st() {
 78     for(int i = 1; i <= n; i++) dp[i][0] = b[i];
 79     int k = int(log(n+1.0)/log(2.0));
 80     for(int j = 1; j <= k; j++) {
 81         for(int i = 1; i + (1 << j) - 1 <= n; i++) {
 82             dp[i][j] = max(dp[i][j-1], dp[i+(1<<(j-1))][j-1]);
 83         }
 84     }
 85 }
 86 
 87 int query(int l, int r) {
 88     int j = int(log(r-l+1.0)/log(2.0));
 89     return max(dp[l][j], dp[r-(1<<j)+1][j]);
 90 }
 91 
 92 int main() {
 93   // FRead();
 94     int l, r;
 95     while(~Rint(n) && n) {
 96         Rint(q);
 97         For(i, 1, n+1) {
 98             Rint(a[i]);
 99             if(i == 1) {
100                 b[i] = 1;
101                 continue;
102             }
103             if(a[i] == a[i-1]) b[i] = b[i-1] + 1;
104             else b[i] = 1;
105         }
106         st();
107         W(q) {
108             scanf("%d%d",&l,&r);
109             int m = l;
110             while(m <= r && a[m] == a[m-1]) m++;
111             int ret = max(query(m, r), m - l);
112             printf("%d
", ret);
113         }
114     }
115     RT 0;
116 }
原文地址:https://www.cnblogs.com/kirai/p/5823300.html