poj 3264 线段树

Posted 2020-08-20

此题为入门级线段树

题意：给定Q（1<=Q<=200000）个数A1A2…AQ，多次求任一区间Ai-Aj中最大数和最小数的差

 1 #include<algorithm>  
 2 #include<cstdio>
 3 #include<string>  
 4 #include<string.h>  
 5 #include<iostream>
 6 using namespace std;
 7 typedef long long LL;
 8 const int INF = 0x7FFFFFFF;
 9 const int maxn = 1e3 + 10;
10 
11 int minV = INF;
12 int maxV = -INF;
13 struct Node
14 {
15     int L, R;
16     int minV, maxV;
17     //Node *pLeft, *pRight;
18     int Mid()
19     {
20         return (L + R) / 2;
21     }
22 };
23 Node tree[800010];//4倍叶子节点的数量就够
24     
25 void BuildTree(int root, int L, int R)
26 {
27     tree[root].L = L;
28     tree[root].R = R;
29     tree[root].minV = INF;
30     tree[root].maxV = -INF;
31     if (L != R)
32     {
33         BuildTree(2 * root + 1, L, (L + R) / 2);
34         BuildTree(2 * root + 2, (L + R) / 2 + 1, R);
35     }
36 }
37 
38 void Insert(int root, int i, int v)
39 //将第i个数，其值为v，插入线段树
40 {
41     if (tree[root].L == tree[root].R)
42     {
43         //成立则亦有tree[root].R==i
44         tree[root].minV = tree[root].maxV = v;
45         return;
46     }
47     tree[root].minV = min(tree[root].minV, v);
48     tree[root].maxV = max(tree[root].maxV, v);
49     if (i <= tree[root].Mid())
50         Insert(2 * root + 1, i, v);
51     else
52         Insert(2 * root + 2, i, v);
53 }
54 
55 void Query(int root, int s, int e)
56 //查询区间[s,e]中的最小值和最大值，如果更优就记在全局变量里
57 {
58     if (tree[root].minV >= minV&&tree[root].maxV <= maxV)
59         return;
60     if (tree[root].L == s&&tree[root].R == e)
61     {
62         minV = min(minV, tree[root].minV);
63         maxV = max(maxV, tree[root].maxV);
64         return;
65     }
66     if (e <= tree[root].Mid())
67         Query(2 * root + 1, s, e);
68     else if (s > tree[root].Mid())
69         Query(2 * root + 2, s, e);
70     else
71     {
72         Query(2 * root + 1, s, tree[root].Mid());
73         Query(2 * root + 2, tree[root].Mid() + 1, e);
74     }
75 }
76 
77 int main()
78 {
79     int n, q, h;
80     int i, j, k;
81     scanf("%d%d", &n, &q);
82     BuildTree(0, 1, n);
83     for (i = 1; i <= n; i++)
84     {
85         scanf("%d", &h);
86         Insert(0, i, h);
87     }
88     for (i = 0; i < q; i++)
89     {
90         int s, e;
91         scanf("%d%d", &s, &e);
92         minV = INF;
93         maxV = -INF;
94         Query(0, s, e);
95         printf("%d\n", maxV - minV);
96     }
97     return 0;
98 }