BZOJ1699: [Usaco2007 Jan]Balanced Lineup排队

description

查询区间最大和最小

题解

线段树

愉悦身心啊

代码

#include<cstring>
#include<cstdio>
#include<algorithm>
#define rd read()
#define lson nd << 1
#define rson nd << 1 | 1
using namespace std;

const int N = 1e5;
const int inf = ~0U >> 1;

int MAX[N << 2], MIN[N << 2], a[N], q, n;

int read() {
    int X = 0, p = 1; char c = getchar();
    for(; c > '9' || c < '0'; c = getchar()) if(c == '-') p = -1;
    for(; c >= '0' && c <= '9';c = getchar()) X = X * 10 + c - '0';
    return X * p;
}

void print(int x) {
    if(x < 0) putchar('-'), x = -x;
    if(x >= 10) print(x / 10);
    putchar(x % 10 + '0');
}

void update(int nd) {
    MIN[nd] = min(MIN[lson], MIN[rson]);
    MAX[nd] = max(MAX[lson], MAX[rson]);
}

void build(int l, int r, int nd) {
    if(l == r) {
        MIN[nd] = MAX[nd] = a[l];
        return;
    }
    int mid = (l + r) >> 1;
    build(l, mid, lson);
    build(mid + 1, r, rson);
    update(nd);
}

int query_max(int L, int R, int l, int r, int nd) {
    if(L <= l && r <= R) return MAX[nd];
    int mid = (l + r) >> 1, tmp = 0;
    if(L <= mid) tmp = max(tmp, query_max(L, R, l, mid, lson));
    if(mid < R) tmp = max(tmp, query_max(L, R, mid + 1, r, rson));
    return tmp;
}

int query_min(int L, int R, int l, int r, int nd) {
    if(L <= l && r <= R) return MIN[nd];
    int mid = (l + r) >> 1, tmp = inf;
    if(L <= mid) tmp = min(tmp, query_min(L, R, l, mid, lson));
    if(mid < R) tmp = min(tmp, query_min(L, R, mid + 1, r, rson));
    return tmp;
}

int main()
{
    n = rd; q = rd;
    for(int i = 1; i <= n; ++i) a[i] = rd;
    build(1, n, 1);
    for(int i = 1; i <= q; ++i) {
        int l = rd, r = rd;
        int mx = query_max(l, r, 1, n, 1), mn = query_min(l, r, 1, n, 1);
        print(mx - mn);
        putchar('
');
    }
}