BZOJ3289 Mato的文件管理

好烦的题，做了我2h，看来蒟蒻就是弱啊。。。

感觉就是莫队算法来着，然后就走上了乱搞的不归路、、、

莫队算法详情请上百度搜索，谢谢!>.<

这道题要求逆序对，所以可以用树状数组动态维护。每次转移复杂度就是树状数组点修改的复杂度，但是转移的时候好烦。。。（一定是我太弱了）

再加上分块，总复杂度为O(n * sqrt(n) * log(n))，刚刚好卡过去。。。

/**************************************************************
    Problem: 3289
    User: rausen
    Language: C++
    Result: Accepted
    Time:8772 ms
    Memory:10200 kb
****************************************************************/
 
#include <cstdio>
#include <cmath>
#include <algorithm>
 
using namespace std;
typedef long long LL;
 
struct data{
    int l, r, wl, w;
    LL ans;
} a[150000];
inline bool cmp(data a, data b){
    return a.wl == b.wl ? a.r < b.r : a.l < b.l;
}
 
inline bool cmp_id(data a, data b){
    return a.w < b.w;
}
 
LL x[150000], y[150000];
LL BIT[150000], rank[150000];
int TOT, T, tot, w[150000], block[150000];
int n, Q, l, r, num;
LL sum;
 
void build(){   
    T = (int) sqrt(n), tot = 0;
    int x = 0;
    while (x < n)
        x += T, w[++tot] = x;
    w[tot] = min(w[tot], n);
    int y = 1;
    for (int i = 1; i <= n; ++i)
        if (i <= w[y]) block[i] = y;
        else block[i] = ++y;
}
 
inline int lowbit(int x){
    return x & (-x);
}
 
LL query(int x){
    if (x < 0) return 0;
    LL res = 0;
    while (x)
        res += BIT[x], x -= lowbit(x);
    return res;
}
 
void change(int x, int del){
    while (x <= n)
        BIT[x] += del, x += lowbit(x);
}
 
void update_right(int p, int del){
    sum += (LL) del * (num - query(x[p])), num += del;
    change(x[p], del);
}
 
void update_left(int p, int del){
    change(x[p], del);  
    sum += (LL) del * query(x[p] - 1), num += del;
}
 
int find(int x){
    int l = 1, r = TOT, mid;
    for (; l != r; ){
        mid = (l + r) >> 1;
        if (rank[mid] >= x) r = mid;
        else l = mid + 1;
    }
    return l;
}
 
int main(){
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i){
        scanf("%lld", x + i);
        y[i] = x[i];
    }
    build();
    sort(y + 1, y + n + 1);
    rank[++TOT] = y[1];
    for (int i = 2; i <= n; ++i)
        if (y[i] != y[i - 1])
            rank[++TOT] = y[i];
    for (int i = 1; i <= n; ++i)
        x[i] = find(x[i]);
     
    scanf("%d", &Q);
    for (int i = 1; i <= Q; ++i){
        scanf("%d%d", &a[i].l, &a[i].r);
        a[i].wl = block[a[i].l], a[i].w = i;
    }
    sort(a + 1, a + Q + 1, cmp);
    l = 1, r = 0, num = sum = 0;
    for (int i = 1; i <= Q; ++i){
        for (; r < a[i].r; ++r) update_right(r + 1, 1);
        for (; r > a[i].r; --r) update_right(r, -1);
        for (; l < a[i].l; ++l) update_left(l, -1);
        for (; l > a[i].l; --l) update_left(l - 1, 1);
        a[i].ans =  a[i].l == a[i].r ? 0 : sum;
    }
     
    sort(a + 1, a + Q + 1, cmp_id);
    for (int i = 1; i <= Q; ++i)
        printf("%lld
", a[i].ans);
    return 0;
}