快速获取区间内的最大最小值（RMQ模板）

原创于 2025-09-21 12:38:44 发布 · 84 阅读

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#RMQ #C++

struct S { int mn, mx; };
auto merge = [&](S &a, S &b) {
     return S { min(a.mn, b.mn), max(a.mx, b.mx) };
};

int MAXP = __lg(n);
S rmq[MAXP + 1][n];
for (int i = 0; i < n; i++) rmq[0][i] = S { nums[i], nums[i] };
for (int p = 1, len = 2; p <= MAXP; p++, len *= 2) for (int i = 0; i + len <= n; i++)
    rmq[p][i] = merge(rmq[p - 1][i], rmq[p - 1][i + len / 2]);

auto query = [&](int l, int r) {
    int p = __lg(r - l + 1);
    return merge(rmq[p][l], rmq[p][r - (1 << p) + 1]);
};

// use
auto s = query(l, r);
auto maxx = s.mx, minn = s.mn;