POJ3264 Balanced Lineup(线段树，区间最值)

题目：

Balanced Lineup Time Limit: 5000MS Memory Limit: 65536KTotal Submissions: 55184 Accepted: 25855Case Time Limit: 2000MS

Description

For the daily milking, Farmer John's N cows (1 ≤ N ≤ 50,000) always line up in the same order. One day Farmer John decides to organize a game of Ultimate Frisbee with some of the cows. To keep things simple, he will take a contiguous range of cows from the milking lineup to play the game. However, for all the cows to have fun they should not differ too much in height.

Farmer John has made a list of Q (1 ≤ Q ≤ 200,000) potential groups of cows and their heights (1 ≤ height ≤ 1,000,000). For each group, he wants your help to determine the difference in height between the shortest and the tallest cow in the group.

Input

Line 1: Two space-separated integers,  N and  Q.  Lines 2.. N+1: Line  i+1 contains a single integer that is the height of cow  i  Lines  N+2.. N+ Q+1: Two integers  A and  B (1 ≤  A ≤  B ≤  N), representing the range of cows from  A to  B inclusive.

Output

Lines 1.. Q: Each line contains a single integer that is a response to a reply and indicates the difference in height between the tallest and shortest cow in the range.

Sample Input

6 3 1 7 3 4 2 5 1 5 4 6 2 2

Sample Output

6 3 0

Source

USACO 2007 January Silver

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思路：

简单的区间最值问题，记录最大值的时候同时记录一下最小值，询问的时候开两个函数，分别询问最大值和最小值。

代码：

#include <cstdio> #include <cstring> #include <cctype> #include <string> #include <set> #include <iostream> #include <stack> #include <cmath> #include <queue> #include <vector> #include <algorithm> #define mem(a,b) memset(a,b,sizeof(a)) #define inf 0x3f3f3f3f #define N 60050 #define ll long long using namespace std; #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 int MAX[N<<2],MIN[N<<2]; void pushup(int rt) { MAX[rt]=max(MAX[rt<<1],MAX[rt<<1|1]); MIN[rt]=min(MIN[rt<<1],MIN[rt<<1|1]); } void build(int l,int r,int rt) { if(l==r) { scanf("%d",&MAX[rt]); MIN[rt]=MAX[rt]; return; } int m=(l+r)>>1; build(lson); build(rson); pushup(rt); } int query1(int L,int R,int l,int r,int rt) { if(L<=l&&r<=R) { return MAX[rt]; } int m=(l+r)>>1; int ret=0; if(L<=m) ret=max(ret,query1(L,R,lson)); if(m<R) ret=max(ret,query1(L,R,rson)); return ret; } int query2(int L,int R,int l,int r,int rt) { if(L<=l&&r<=R) { return MIN[rt]; } int m=(l+r)>>1; int ret=inf; if(L<=m) ret=min(ret,query2(L,R,lson)); if(m<R) ret=min(ret,query2(L,R,rson)); return ret; } int main() { int n,q,a,b; while(~scanf("%d%d",&n,&q)) { mem(MAX,0); build(1,n,1); while(q--) { scanf("%d%d",&a,&b); printf("%d\n",query1(a,b,1,n,1)-query2(a,b,1,n,1)); } } return 0; }