POJ3264

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<span style="color:#3366ff;">/*********************************************************************
    author    :   Grant Yuan
    time      :   2014.7.26
    algorithm :   线段树

**********************************************************************/
#include <iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#define MAX 50003
#define INF 999999999
using namespace std;
int n,m;
struct node{
int l;
int r;
int Min;
int Max;
};
int m1,m2;
node tree[4*MAX];
int h[MAX];

void build(int left,int right,int root)
{
     tree[root].l=left;
     tree[root].r=right;

    if(left==right){
     tree[root].Max=h[left];
     tree[root].Min=h[left];
    return;
    }
    int mid=(left+right)>>1;
    build(left,mid,root*2);
    build(mid+1,right,root*2+1);
    tree[root].Max=max(tree[root*2].Max,tree[root*2+1].Max);
    tree[root].Min=min(tree[root*2].Min,tree[root*2+1].Min);
}

void findMax(int left,int right,int root)
{
   if(left<=tree[root].l&&right>=tree[root].r)
   {m1=max(m1,tree[root].Max);
   return;}
    int mid=(tree[root].l+tree[root].r)>>1;
    if(mid>=right)
        findMax(left,right,root*2);
    else if(mid<left)
        findMax(left,right,root*2+1);
    else{
        findMax(left,right,2*root);
        findMax(left,right,2*root+1);
    }
}

void findMin(int left,int right,int root)
{
    if(left<=tree[root].l&&right>=tree[root].r)
      {m2=min(m2,tree[root].Min);
      return;}
    int mid=(tree[root].l+tree[root].r)>>1;
    if(mid>=right)
        findMin(left,right,root*2);
    else if(mid<left)
        findMin(left,right,root*2+1);
    else{
       findMin(left,right,2*root);
       findMin(left,right,2*root+1);

    }
}

int main()
{
  cin>>n>>m;int a,b;
  for(int i=1;i<=n;i++)
    scanf("%d",&h[i]);

    build(1,n,1);

    for(int i=0;i<m;i++)
        {scanf("%d%d",&a,&b); m1=0;m2=INF;

     findMax(a,b,1);
       findMin(a,b,1);
        printf("%d\n",m1-m2);
        }
    return 0;
}
</span>

POJ3264

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原文地址：http://blog.csdn.net/yuanchang_best/article/details/38148561