CF 220E, 树状数组

维护逆序对的树状数组瓜题，就不报告了（手抖强行wa两发）

#include <cstdio>
#include <string>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <complex>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <deque>
#include <ctime>

using namespace std;

const double EPS = 1e-8;

#define ABS(x) ((x)<0?(-(x)):(x))
#define SQR(x) ((x)*(x))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))

#define LSON(x) ((x)<<1)
#define RSON(x) (((x)<<1)+1)
#define LOWBIT(x) ((x)&(-(x)))
#define MAXS 1111
#define MAXN 222222
#define VOIDPOINT 0
#define LL long long
#define OO 214748364

struct TreeArray{
    int tree[MAXN], n;
    int f[MAXN];
    void clear(int nn = MAXN - 20) {
        n = nn;
        memset(tree, 0, sizeof(tree[0])*(n+10));
        memset(f, 0, sizeof(f[0])*(n+10));
    }
    void add(int x, int num = 1) {
        if (x < 1) puts("Error in TreeArray, x must > 0!!");
        f[x] += num;
        while (x <= n) {
            tree[x] += num;
            x += LOWBIT(x);
        }
    }
    int get(int x) {
        int res = 0;
        while (x > 0) {
            res += tree[x];
            x -= LOWBIT(x);
        }
        return res;
    }
    int getright(int x) { // get [x ~ n]
        return get(n) - get(x-1);
    }
    int take(int x, int k) { //树状数组二分前面第k个1的位置尝试，类似区间查询
        int res = 0, sum = 0;
        sum = get(x);
        while (sum) {
            if (sum == k && f[x]) {
                res = x; break;
            }
            if (sum - tree[x] >= k) {
                sum -= tree[x];
                x -= LOWBIT(x);
            } else {
                if (f[x]) sum -= f[x];
                --x;
            }
        }
        add(res, -1);
        return res;
    }
} TreeL, TreeR;

int a[MAXN];
vector <int > lsh;
LL ans, n, k;

void init() {
    lsh.clear();
    for (int i = 0; i < n; ++i) {
        scanf("%d", a+i);
        lsh.push_back(a[i]);
    }
    sort(lsh.begin(), lsh.end());
    lsh.erase(unique(lsh.begin(), lsh.end()), lsh.end());
    for (int i = 0; i < n; ++i) a[i] = lower_bound(lsh.begin(), lsh.end(), a[i]) - lsh.begin() + 1;
}

void solve() {
    ans = 0;
    int sum = 0, head = 0, tail = n;
    TreeL.clear(n); TreeR.clear(n);
    TreeL.add(a[0]); 
    while (head + 1 < tail && 
    sum + TreeL.getright(a[tail-1]+1) + TreeR.get(a[tail-1]-1) <= k) {
        sum += TreeL.getright(a[tail-1]+1) + TreeR.get(a[tail-1]-1);
        --tail;
        TreeR.add(a[tail]);
    }

    ans += n - tail;


    for (head = 1; head < n; ++head) {
        if (head == tail) {
            sum -= (TreeL.getright(a[tail]+1) + TreeR.get(a[tail]-1));
            TreeR.add(a[tail++], -1);
        }
        TreeL.add(a[head]);
        sum += TreeL.getright(a[head]+1) + TreeR.get(a[head]-1); 
        while (sum > k && tail < n) {
            sum -= TreeL.getright(a[tail]+1) + TreeR.get(a[tail]-1);
            TreeR.add(a[tail++], -1);
        }
        ans += n - tail;
    }
}

int main() {
//    freopen("test.txt", "r", stdin);
    while (cin >> n >> k) {
        init();
        solve();
        cout << ans << endl;
    }
    return 0;
}