POJ 3264 Balanced Lineup【线段树区间查询求最大值和最小值】

 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <string.h>
 4 using namespace std;
 5 #define maxsize 200020
 6 typedef struct
 7 {
 8     int left,right;
 9     int maxn;
10     int minn;
11 }Node;
12 int n,m;
13 int Max,Min;
14 int num[maxsize];
15 Node tree[maxsize*20];
16 inline void buildtree(int root,int left,int right)// 构建线段树
17 {
18     int mid;
19     tree[root].left=left;
20     tree[root].right=right;// 当前节点所表示的区间
21     if(left==right)// 左右区间相同，则此节点为叶子，max 应储存对应某个学生的值
22     {
23         tree[root].maxn=num[left];
24         tree[root].minn=num[left];
25         return;
26     }
27     mid=(left+right)/2;
28     //int a,b;// 递归建立左右子树，并从子树中获得最大值
29     buildtree(2*root,left,mid);
30     buildtree(2*root+1,mid+1,right);
31     tree[root].maxn=max(tree[root*2].maxn,tree[root*2+1].maxn);
32     tree[root].minn=min(tree[root*2].minn,tree[root*2+1].minn);
33 }
34 inline void find(int root,int left,int right)// 从节点 root 开始，查找 left 和 right 之间的最大值
35 {
36     int mid;
37     //if(tree[root].left>right||tree[root].right<left)// 若此区间与 root 所管理的区间无交集
38         //return;
39     if(left==tree[root].left&&tree[root].right==right)// 若此区间包含 root 所管理的区间
40     {
41         Max=max(tree[root].maxn,Max);
42         Min=min(tree[root].minn,Min);
43         return;
44     }
45     mid=(tree[root].left+tree[root].right)/2;
46     if(right<=mid)
47         find(root*2,left,right);
48     else if(left>mid)
49         find(root*2+1,left,right);
50     else
51     {
52         find(root*2,left,mid);
53         find(root*2+1,mid+1,right);
54         //tree[root].maxn=max(tree[root*2].maxn,tree[root*2+1].maxn);
55         //tree[root].minn=min(tree[root*2].minn,tree[root*2+1].minn);
56         //return;
57     }
58 }
59 
60 int main()
61 {
62     //char c;
63     int i;
64     int x,y;
65     //scanf("d%d",&n,&m);
66     while(scanf("%d%d",&n,&m)!=EOF)
67     {
68         for(i=1;i<=n;i++)
69             scanf("%d",&num[i]);
70         buildtree(1,1,n);
71         for(i=1;i<=m;i++)
72         {
73             //getchar();
74             Max=-99999999999;
75             Min= 99999999999;
76             scanf("%d%d",&x,&y);
77             //if(c==‘Q‘)
78                 //printf("%d\n",find(1,x,y));
79             //else
80             //{
81                // num[x]=y;
82                // update(1,x,y);
83             //}
84             find(1,x,y);
85             printf("%d\n",Max-Min);
86         }
87     }
88     return 0;
89 }