UVA 11990 ``Dynamic'' Inversion

#include<bits/stdc++.h>
using namespace std;


const int maxn = 2e5+5, LogN = 20;

typedef long long ll;
ll invPair;
int a[maxn],p[maxn];
int iv[maxn];
int n;

int s[maxn<<2];
int C[LogN][maxn];
int Set[LogN][maxn];

#define para int o = 1, int l = 1,int r = n,int dep = 0
#define lo (o<<1)
#define ro (o<<1|1)
#define TEMP int mid = (l+r)>>1, lc = lo, rc = ro;
#define lsn lc, l, mid, dep+1
#define rsn rc, mid+1, r, dep+1

#define lb(x) ((x)&-(x))
int sum(int C[],int x)
{
    int re = 0;
    while(x>0){
        re += C[x];
        x -= lb(x);
    }
    return re;
}

void add(int C[],int x,int d,int r)
{
    while(x<=r){
        C[x] += d;
        x += lb(x);
    }
}

int qpos;
int ql,qr,val;
void queryPrefix(para)
{
    if(1<=l&&r<=qr){
        int pos = upper_bound(Set[dep]+l,Set[dep]+r+1,val)-Set[dep]-l;//等于等于val的最大元素的编号
        invPair += s[o] - sum(C[dep]+l-1,pos);//得到大于val的元素个数
    }else {
        TEMP
        queryPrefix(lsn);
        if(qr>mid) queryPrefix(rsn);
    }
}

void querySuffix(para)
{
    if(ql<=l&&r<=n){
        int pos = lower_bound(Set[dep]+l,Set[dep]+r+1,val)-Set[dep]-l;//严格小于val的元素的编号
        invPair += sum(C[dep]+l-1,pos);
    }else {
        TEMP
        if(ql<=mid) querySuffix(lsn);
        querySuffix(rsn);
    }
}


void modify(para)
{
    s[o]++;
    if(l == r){
        C[dep][l] = 1;
    }else{
        TEMP
        if(qpos<=mid) modify(lsn);
        else modify(rsn);
        int pos = upper_bound(Set[dep]+l,Set[dep]+r+1,val)-Set[dep]-l;//val在set里，从1开始编号
        add(C[dep]+l-1,pos,1,r-l+1);//l-1是0号位，容纳r-l+1个元素
    }
}


//为保证BIT之间互不影响，merge_sort离散,同时计算逆序对
void discretize(para)
{
    s[o] = 0;
    memset(C[dep]+l,0,sizeof(int)*(r-l+1));
    if(l == r) {
        Set[dep][l] = a[l];
        return;
    }else {
        TEMP;
        discretize(lsn);
        discretize(rsn);
        int p = l, q = mid+1, k = l;
        while(p<=mid || q<=r){
            if(q > r|| (p <= mid && Set[dep+1][p] <= Set[dep+1][q]) ){
                iv[Set[dep+1][p]] += k-p;//和后面的数构成逆序对
                Set[dep][k++] = Set[dep+1][p++];
            }else {
                iv[Set[dep+1][q]] += mid-p+1;//和前面的数构成逆序对
                Set[dep][k++] = Set[dep+1][q++];
            }
        }
    }
}

//#define LOCAL
int main()
{
#ifdef LOCAL
    freopen("in.txt","r",stdin);
#endif
    int m;
    while(~scanf("%d%d",&n,&m)){
        memset(iv+1,0,sizeof(int)*n);
        for(int i = 1; i <= n; i++){
            scanf("%d",a+i);
            p[a[i]] = i;
        }
        invPair = 0;
        discretize();
        for(int i = 1; i <= n; i++){
            invPair += iv[i];
        }
        invPair >>= 1;
        while(m--){
            scanf("%d",&val);
            printf("%lld\n",invPair);
            invPair -= iv[val];
            qr = p[val]-1;
            ql = p[val]+1;
            if(qr>=1) queryPrefix();
            if(ql<=n) querySuffix();
            qpos = p[val];
            modify();
        }
    }
    return 0;
}