Balanced Lineup

Time Limit: 5000MS		Memory Limit: 65536K
Total Submissions: 42349		Accepted: 19917
Case Time Limit: 2000MS

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.

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.

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.

6 3

1

7

3

4

2

5

1 5

4 6

2 2

6

3

0
线段树维护区间最大值、最小值，然后相减。AC代码：

 #include <iostream>

 #include <algorithm>

 #include <cstdio>

 #include <map>

 #include <string>

 #include <string.h>

 #include <queue>

 #include <vector>

 #include <set>

 #include <cmath>

 #define inf 0x7fffffff

 using namespace std;

 const int maxn=;

 struct b{

 int imax,imin;

 }tree[maxn*+];

 int n,q,x,y,a[maxn+];

 void build(int p,int l,int r){

      if(l==r) {tree[p].imax=a[l],tree[p].imin=a[l];return ;}

      int mid=(l+r)/;

      build(p*,l,mid);

      build(p*+,mid+,r);

      tree[p].imax=max(tree[p*].imax,tree[p*+].imax);

      tree[p].imin=min(tree[p*].imin,tree[p*+].imin);

 }

 int findmin(int p,int l,int r,int x,int y){

      if(x<=l&&r<=y) return tree[p].imin;

      int mid=(l+r)/;

      if(x>mid) return findmin(p*+,mid+,r,x,y);

      if(y<=mid) return findmin(p*,l,mid,x,y);

      return min(findmin(p*+,mid+,r,x,y),findmin(p*,l,mid,x,y));

 }

 int findmax(int p,int l,int r,int x,int y){

      if(x<=l&&r<=y) return tree[p].imax;

      int mid=(l+r)/;

      if(x>mid) return findmax(p*+,mid+,r,x,y);

      if(y<=mid) return findmax(p*,l,mid,x,y);

      return max(findmax(p*+,mid+,r,x,y),findmax(p*,l,mid,x,y));

 }

 int main()

 {

     scanf("%d%d",&n,&q);

     for(int i=;i<=n;i++)

         scanf("%d",&a[i]);

         build(,,n);

     for(int i=;i<=q;i++){

         scanf("%d%d",&x,&y);

         printf("%d\n",findmax(,,n,x,y)-findmin(,,n,x,y));

     }

     return ;

 }