cychester

BZOJ1699: [Usaco2007 Jan]Balanced Lineup排队 - 线段树

description

查询区间最大和最小

题解

线段树

愉悦身心啊

代码

 1 #include<cstring>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #define rd read()
 5 #define lson nd << 1
 6 #define rson nd << 1 | 1
 7 using namespace std;
 8 
 9 const int N = 1e5;
10 const int inf = ~0U >> 1;
11 
12 int MAX[N << 2], MIN[N << 2], a[N], q, n;
13 
14 int read() {
15     int X = 0, p = 1; char c = getchar();
16     for(; c > '9' || c < '0'; c = getchar()) if(c == '-') p = -1;
17     for(; c >= '0' && c <= '9';c = getchar()) X = X * 10 + c - '0';
18     return X * p;
19 }
20 
21 void print(int x) {
22     if(x < 0) putchar('-'), x = -x;
23     if(x >= 10) print(x / 10);
24     putchar(x % 10 + '0');
25 }
26 
27 void update(int nd) {
28     MIN[nd] = min(MIN[lson], MIN[rson]);
29     MAX[nd] = max(MAX[lson], MAX[rson]);
30 }
31 
32 void build(int l, int r, int nd) {
33     if(l == r) {
34         MIN[nd] = MAX[nd] = a[l];
35         return;
36     }
37     int mid = (l + r) >> 1;
38     build(l, mid, lson);
39     build(mid + 1, r, rson);
40     update(nd);
41 }
42 
43 int query_max(int L, int R, int l, int r, int nd) {
44     if(L <= l && r <= R) return MAX[nd];
45     int mid = (l + r) >> 1, tmp = 0;
46     if(L <= mid) tmp = max(tmp, query_max(L, R, l, mid, lson));
47     if(mid < R) tmp = max(tmp, query_max(L, R, mid + 1, r, rson));
48     return tmp;
49 }
50 
51 int query_min(int L, int R, int l, int r, int nd) {
52     if(L <= l && r <= R) return MIN[nd];
53     int mid = (l + r) >> 1, tmp = inf;
54     if(L <= mid) tmp = min(tmp, query_min(L, R, l, mid, lson));
55     if(mid < R) tmp = min(tmp, query_min(L, R, mid + 1, r, rson));
56     return tmp;
57 }
58 
59 int main()
60 {
61     n = rd; q = rd;
62     for(int i = 1; i <= n; ++i) a[i] = rd;
63     build(1, n, 1);
64     for(int i = 1; i <= q; ++i) {
65         int l = rd, r = rd;
66         int mx = query_max(l, r, 1, n, 1), mn = query_min(l, r, 1, n, 1);
67         print(mx - mn);
68         putchar('\n');
69     }
70 }
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posted on 2018-08-22 10:31  cychester  阅读(107)  评论(0编辑  收藏  举报

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