[Usaco2007 Jan]Balanced Lineup

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一道RMQ板子题，分别维护最大值和最小值，不解释。

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<cstdlib>
 7 #include<cctype>
 8 #include<stack>
 9 #include<queue>
10 #include<vector>
11 using namespace std;
12 #define enter puts("")
13 #define space putchar(' ')
14 #define Mem(a) memset(a, 0, sizeof(a))
15 typedef long long ll;
16 typedef double db;
17 const int INF = 0x3f3f3f3f;
18 const db eps  =1e-8;
19 const int maxn = 5e4 + 5;
20 inline ll read()
21 {
22     ll ans = 0;
23     char ch = getchar(), last = ' ';
24     while(!isdigit(ch)) {last = ch; ch = getchar();}
25     while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();}
26     if(last == '-') ans = -ans;
27     return ans;
28 }
29 inline void write(ll x)
30 {
31     if(x < 0) putchar('-'), x = -x;
32     if(x >= 10) write(x / 10);
33     putchar(x % 10 + '0');
34 }
35 
36 int n, m, a[maxn];
37 
38 int dp[maxn][20][2], b[maxn];
39 void RMQ()
40 {
41     for(int i = 1; i <= n; ++i) dp[i][0][0] = dp[i][0][1] = a[i];
42     for(int j = 1; (1 << j) <= n; ++j)
43         for(int i = 1; i + (1 << j) - 1 <= n; ++i)
44         {
45             dp[i][j][0] = max(dp[i][j - 1][0], dp[i + (1 << (j - 1))][j - 1][0]);
46             dp[i][j][1] = min(dp[i][j - 1][1], dp[i + (1 << (j - 1))][j - 1][1]);
47         }
48     int x = 0;
49     for(int i = 1; i <= n; ++i)
50     {
51         b[i] = x;
52         if((1 << (x + 1)) <= (i + 1)) x++;
53     }
54 }
55 int query(int L, int R, bool flag)
56 {
57     int k = b[R - L + 1];
58     if(flag) return min(dp[L][k][flag], dp[R - (1 << k) + 1][k][flag]);    //应该是R - (1 << k) + 1,不是R - k + 1…… 
59     else return max(dp[L][k][flag], dp[R - (1 << k) + 1][k][flag]);
60 }
61 
62 
63 int main()
64 {
65     n = read(); m = read();
66     for(int i = 1; i <= n; ++i) a[i] = read();
67     RMQ();
68     for(int i = 1; i <= m; ++i)
69     {
70         int L = read(), R = read();
71         write(query(L, R, 0) - query(L, R, 1)); enter;
72     }
73     return 0;
74 }

标签：10,ch,int,ll,Jan,include,ans,Balanced,Lineup
来源： https://blog.51cto.com/u_15234622/2830836