Poj 3246 Balanced Lineup（线段树基础）

依旧是线段树基础题

询问区间的最大值和最小值之差，只有询问，没有插入删除。继续理解基础线段树

 

#include <iostream>

#include <algorithm>

#include <cmath>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <string>

#include <vector>

#include <set>

#include <map>

#include <queue>

#include <stack>

#include <climits>//形如INT_MAX一类的

#define MAX 50005

#define INF 0x7FFFFFFF

#define REP(i,s,t) for(int i=(s);i<=(t);++i)

#define ll long long

#define mem(a,b) memset(a,b,sizeof(a))

#define mp(a,b) make_pair(a,b)

#define L(x) x<<1

#define R(x) x<<1|1

# define eps 1e-5

//#pragma comment(linker, "/STACK:36777216") ///传说中的外挂

using namespace std;

struct node

{

    int l,r,mid,max,min;

}tree[4*MAX];

int hei[MAX],a,b;

int maxx(int a,int b) {

    if(a > b) return a;

        return b;

}

int minn(int a,int b) {

    if(a < b) return a;

        return b;

}

void up(int num) {

    if(tree[num].max < tree[L(num)].max) tree[num].max = tree[L(num)].max;

    if(tree[num].max < tree[R(num)].max) tree[num].max = tree[R(num)].max;

    if(tree[num].min > tree[L(num)].min) tree[num].min = tree[L(num)].min;

    if(tree[num].min > tree[R(num)].min) tree[num].min = tree[R(num)].min;

}



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

    tree[num].l = l;

    tree[num].r = r;

    tree[num].mid = (l + r) >> 1;

    tree[num].max = 0;

    tree[num].min = INF;

    if(l == r) {

        tree[num].max = hei[l];

        tree[num].min = hei[l];



        return ;

    }

    build(l,tree[num].mid ,L(num));

    build(tree[num].mid+1,r,R(num));



    up(num);

}



void query(int l,int r,int num) {

    if(l <= tree[num].l && r >= tree[num].r) {

        a = maxx(a,tree[num].max);

        b = minn(b,tree[num].min);

        return ;

    }



    if(r <= tree[num].mid ) {

        query(l,r,L(num));

    }

    else if(l > tree[num].mid) {

        query(l,r,R(num));

    }

    else {

        query(l,tree[num].mid,L(num));

        query(tree[num].mid + 1,r,R(num));

    }

}



void test(int n)

{

    for(int i=1; i<=2*n+1; i++){

        printf("l:%d r:%d max:%d min:%d\n",tree[i].l,tree[i].r,tree[i].max,tree[i].min);

    }

}



int main() {



    int n,q,i;

    int l,r;

    cin >> n >> q;

    for(i=1; i<=n; i++) {

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

    }

    build(1,n,1);

    //test(n);

    for(i=1; i<=q; i++) {

        a = 0;

        b = INF;

        scanf("%d%d",&l,&r);

        query(l,r,1);

        printf("%d\n",a - b);

    }

    return 0;

}