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;}