poj3264（线段树求区间最大最小值）

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题目链接:poj3264

简单题，求区间最大值和最小值

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;#define N 1000010int n,a[N];int ans_x, ans_y;struct node{    int r,l;    int maxx,minn;}s[N<<2];void build(int l, int r, int n){    s[n].l = l;    s[n].r = r;    s[n].maxx = 0;    s[n].minn = N;    if(l == r)    {        s[n].maxx = s[n].minn = a[l];        return;    }    int mid = (l + r) >> 1;    build(l, mid, n<<1);    build(mid + 1, r, n<<1|1);    s[n].maxx = max(s[n<<1].maxx, s[n<<1|1].maxx);    s[n].minn = min(s[n<<1].minn, s[n<<1|1].minn);}void query(int l, int r, int n){    if(s[n].l == l && s[n].r == r)    {        ans_x = max(ans_x, s[n].maxx);        ans_y = min(ans_y, s[n].minn);        return;    }    int mid = (s[n].l + s[n].r) >> 1;    if(r <= mid)        query(l, r, n<<1);    else if(l > mid)        query(l, r, n<<1|1);    else    {        query(l, mid, n<<1);        query(mid+1, r, n<<1|1);    }}int main(){    int m,t,i,x,y;    while(~scanf("%d%d",&m,&t))    {        for(i = 1; i <= m; i ++)            scanf("%d",&a[i]);        build(1,m,1);        while(t--)        {            scanf("%d%d",&x,&y);            ans_x = 0;            ans_y = N;            query(x,y,1);            printf("%d\n",ans_x-ans_y);        }    }    return 0;}