python/TangDou/AcWing/BIT/POJ3264_SZSZ.cpp

#include <algorithm>
#include <cstdio>
#include <cstring>

const int INF = 0x3f3f3f3f;
using namespace std;
const int N = 50010;

int a[N];
int n, q;

// 树状数组模板
int c1[N], c2[N]; // c1:维护最大值，c2：维护最小值

int lowbit(int x) {
    return x & -x;
}

void update(int x, int d) {
    for (int i = x; i < N; i += lowbit(i)) c1[i] = max(c1[i], d), c2[i] = min(c2[i], d);
}

int query(int x, int y) {
    int mx = 0, mi = INF;
    while (y >= x) {                            // 右侧到左侧
        mx = max(mx, a[y]), mi = min(mi, a[y]); // 每次最后侧的点参加评比

        for (--y; y - x >= lowbit(y); y -= lowbit(y)) // 从x~y-1检查每个片断
            mx = max(mx, c1[y]), mi = min(mi, c2[y]);
    }
    return mx - mi;
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("POJ3264.in", "r", stdin);
#endif
    memset(c1, 0, sizeof c1);
    memset(c2, 0x3f, sizeof c2); // 最小值，需要先设置最大，最大值默认的就是0，不需要设置
    scanf("%d %d", &n, &q);

    for (int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
        update(i, a[i]);
    }

    while (q--) {
        int a, b;
        scanf("%d %d", &a, &b);
        printf("%d\n", query(a, b));
    }
    return 0;
}