[POJ3264]Balanced Lineup（线段树，区间最值差）

题目链接：http://poj.org/problem?id=3264

一排牛按1~n标号记录重量，问每个区间最重的和最轻的差值。

线段树维护当前节点下属叶节点的两个最值，查询后作差即可。

 #include <algorithm>
 #include <iostream>
 #include <iomanip>
 #include <cstring>
 #include <climits>
 #include <complex>
 #include <fstream>
 #include <cassert>
 #include <cstdio>
 #include <bitset>
 #include <vector>
 #include <deque>
 #include <queue>
 #include <stack>
 #include <ctime>
 #include <set>
 #include <map>
 #include <cmath>

 using namespace std;

 #define lson l, m, rt << 1
 #define rson m + 1, r, rt << 1 | 1
 typedef pair<int, int> pii;
 const int maxn = ;
 int n, q, a, b;
 pii node[maxn<<];

 void pushUP(int rt) {
     int ll = min(node[rt<<].first, node[rt<<|].first);
     int rr = max(node[rt<<].second, node[rt<<|].second);
     node[rt] = pii(ll, rr);
 }

 void build(int l, int r, int rt) {
     if(l == r) {
         scanf("%d", &node[rt].first);
         node[rt].second = node[rt].first;
         return;
     }
     int m = (l + r) >> ;
     build(lson);
     build(rson);
     pushUP(rt);
 }

 int querymax(int L, int R, int l, int r, int rt) {
     if(L <= l && r <= R) {
         return node[rt].second;
     }
     int m = (l + r) >> ;
     int ans = -;
     if(L <= m) ans = max(ans, querymax(L, R, lson));
     if(m < R) ans = max(ans, querymax(L, R, rson));
     return ans;
 }

 int querymin(int L, int R, int l, int r, int rt) {
     if(L <= l && r <= R) {
         return node[rt].first;
     }
     int m = (l + r) >> ;
     int ans = 0x7f7f7f;
     if(L <= m) ans = min(ans, querymin(L, R, lson));
     if(m < R) ans = min(ans, querymin(L, R, rson));
     return ans;
 }

 int main() {
     // freopen("in", "r", stdin);
     while(~scanf("%d %d", &n, &q)) {
         build(, n, );
         while(q--) {
             scanf("%d %d", &a, &b);
             int ll = querymin(a, b, , n, );
             int rr = querymax(a, b, , n, );
             printf("%d\n", rr - ll);
         }
     }
     return ;
 }