BZOJ 3289 Mato的文件管理

莫队算法+树状数组转移

#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#include<algorithm>
using namespace std;

const int maxn = 50000 + 10;
int n, m;
int tmp[maxn], a[maxn], lsh[maxn], cnt;
int pos[maxn];
int c[maxn];
long long ans[maxn], Ans;
int L, R;

struct X
{
    int l, r, id;
}s[maxn];

int f(int x)
{
    int l = 1, r = cnt;
    while (l <= r)
    {
        int mid = (l + r) / 2;
        if (lsh[mid] < x) l = mid + 1;
        else if (lsh[mid]>x) r = mid - 1;
        else return mid;
    }
}

void LSH()
{
    sort(tmp + 1, tmp + 1 + n);
    cnt = 0, lsh[++cnt] = tmp[1];
    for (int i = 2; i <= n; i++)
    {
        if (tmp[i] == tmp[i - 1]) continue;
        lsh[++cnt] = tmp[i];
    }
    for (int i = 1; i <= n; i++) a[i] = f(a[i]);
}

bool cmp(const X&a, const X&b)
{
    if (pos[a.l] == pos[b.l]) return a.r < b.r;
    return a.l < b.l;
}

int lowbit(int x) { return x&(-x); }
void update(int pos, int val)
{
    while (pos <= cnt) 
        c[pos] = c[pos] + val, pos = pos + lowbit(pos);
}
int getsum(int pos)
{
    int res = 0;
    while (pos > 0) 
        res = res + c[pos], pos = pos - lowbit(pos); 
    return res;
}

int main()
{
    while (~scanf("%d", &n)) {
        int sz = sqrt(n);
        for (int i = 1; i <= n; i++)
        {
            pos[i] = i / sz;
            scanf("%d", &tmp[i]);
            a[i] = tmp[i];
        }
        LSH();

        scanf("%d", &m);
        for (int i = 1; i <= m; i++) {
            scanf("%d%d", &s[i].l, &s[i].r);
            s[i].id = i;
        }
        sort(s + 1, s + 1 + m, cmp);

        for (int i = s[1].l; i <= s[1].r; i++)
        {
            int sum = getsum(cnt) - getsum(a[i]);
            Ans = Ans + (long long)sum;
            update(a[i], 1);
        }
        ans[s[1].id] = Ans; L = s[1].l; R = s[1].r;

        for (int i = 2; i <= m; i++)
        {
            while (L < s[i].l)
            {
                int sum = getsum(a[L] - 1);
                Ans = Ans - (long long)sum;
                update(a[L], -1);
                L++;
            }
            while (L > s[i].l)
            {
                L--;
                int sum = getsum(a[L] - 1);
                Ans = Ans + (long long)sum;
                update(a[L], 1);
            }
            while (R < s[i].r)
            {
                R++;
                int sum = getsum(cnt) - getsum(a[R]);
                Ans = Ans + (long long)sum;
                update(a[R], 1);
            }
            while (R > s[i].r)
            {
                int sum = getsum(cnt) - getsum(a[R]);
                Ans = Ans - (long long)sum;
                update(a[R], -1);
                R--;
            }
            ans[s[i].id] = Ans;
        }

        for (int i = 1; i <= m; i++) printf("%lld\n", ans[i]);
    }
    return 0;
}