• [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 }
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  • 原文地址:https://www.cnblogs.com/kirai/p/5823300.html
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