Luogu 3759 [TJOI2017]不勤劳的图书管理员

再也不作死写FhqTreap作内层树了，卡的不如暴力呜呜呜…… 

题意翻译：给一个序列，每个下标包含两个属性$a$和$v$，求第一个属性与下标形成的所有逆序对的第二个属性和，给出$m$个交换两个下标的操作，每次操作之后查询。

考虑一下交换之后会发生什么：

假设这次要交换$x$和$y$，使$x leq y$。

发现交换之后$x, y$和$x$的左边的数和$y$右边的数构成的逆序对产生的贡献不变，发生变化的是中间的数。

那么问题就简单了，只要先消去中间的数和$x, y$的贡献，具体来说就是$[x + 1, y - 1]$这个区间中$a_{i}$比$a_{x}$小的$b_{i}$和，以及$a_{i}$比$a_{y}$大的$b_{i}$和。

发现$(x, y)$可能也会构成一个逆序对，拎出来判一下可以保证这一对只被计算一次。

然后算一下交换之后产生的贡献，方法类似。

树套树维护即可。

时间复杂度$O(nlog^{2}n)$。

Code：

#include <cstdio>
#include <cstring>
using namespace std;
typedef long long ll;

const int N = 5e4 + 5;
const int M = 2e7 + 5;
const ll P = 1e9 + 7;

int n, m, a[N];
ll v[N], ans = 0LL;

template <typename T>
inline void read(T &X) {
    X = 0; char ch = 0; T op = 1;
    for(; ch > '9' || ch < '0'; ch = getchar())
        if(ch == '-') op = -1;
    for(; ch >= '0' && ch <= '9'; ch = getchar())
        X = (X << 3) + (X << 1) + ch - 48;
    X *= op;
}

template <typename T>
inline void swap(T &x, T &y) {
    T t = x; x = y; y = t;
}

namespace BinaryIndexTree {
    int cnt[N]; ll s[N];
    
    #define lowbit(x) (x & (-x))
    
    inline void modifyS(int p, ll val) {
        for(; p <= n; p += lowbit(p)) s[p] = (s[p] + val) % P;
    }
    
    inline void modifyC(int p) {
        for(; p <= n; p += lowbit(p)) cnt[p]++;
    }
    
    inline ll getSum(int p) {
        ll res = 0;
        for(; p > 0; p -= lowbit(p)) res = (res + s[p]) % P;
        return res;
    }
    
    inline int getCnt(int p) {
        int res = 0;
        for(; p > 0; p -= lowbit(p)) res += cnt[p];
        return res;
    }
    
    #undef lowbit
    
} using namespace BinaryIndexTree;

namespace Tree {
    int nodeCnt, root[N * 30];
    struct Node {
        int lc, rc, siz;
        ll sum;
    } s[M];
    
    #define mid ((l + r) >> 1)
    
    inline void up(int p) {
        if(!p) return;
        s[p].siz = s[s[p].lc].siz + s[s[p].rc].siz;
        s[p].sum = (s[s[p].lc].sum + s[s[p].rc].sum) % P;
    }
    
    void modify(int &p, int l, int r, int x, ll selV) {
        if(!p) p = ++nodeCnt;
        if(l == r) {
            s[p].siz = (selV != -1);
            s[p].sum = (selV == -1 ? 0 : selV % P);
            return;
        }
        
        if(x <= mid) modify(s[p].lc, l, mid, x, selV);
        else modify(s[p].rc, mid + 1, r, x, selV);
        up(p);
    }
    
    ll query(int p, int l, int r, int x, int y, ll selV) {
        if(!p) return 0LL;
        if(x <= l && y >= r) return (selV * s[p].siz % P + s[p].sum) % P;
        
        ll res = 0LL;
        if(x <= mid) res = (res + query(s[p].lc, l, mid, x, y, selV)) % P;
        if(y > mid) res = (res + query(s[p].rc, mid + 1, r, x, y, selV)) % P;
        return res;
    }
    
    #define lowbit(p) (p & (-p))
    
    inline void change(int p, int val, ll selV) {
        for(; p <= n; p += lowbit(p))
            modify(root[p], 1, n, val, selV);
    }
    
    inline void clear(int p, int val) {
        for(; p <= n; p += lowbit(p))
            modify(root[p], 1, n, val, -1);
    }
    
    inline ll ask(int p, int v, ll selV, int type) {
        ll res = 0LL;
        for(; p > 0; p -= lowbit(p)) {
            if(type) res = (res + query(root[p], 1, n, v + 1, n, selV)) % P;
            else res = (res + query(root[p], 1, n, 1, v - 1, selV)) % P;
        }
        return res;
    }
    
    inline ll qSum(int l, int r, int v, ll selV, int type) {
        return (ask(r, v, selV, type) - ask(l - 1, v, selV, type) + P) % P;
    }
    
} using namespace Tree;

int main() {
    read(n), read(m);
    nodeCnt = 0;
    for(int i = 1; i <= n; i++) {
        read(a[i]), read(v[i]);
        ans = (ans + (getSum(n) - getSum(a[i]) + P) % P + P + v[i] * (getCnt(n) - getCnt(a[i])) % P + P) % P;
        modifyS(a[i], v[i]), modifyC(a[i]);
        change(i, a[i], v[i]);
    }
    
    for(int x, y; m--; ) {
        read(x), read(y);
        if(x == y) {
            printf("%lld
", ans);
            continue;
        }
        if(x > y) swap(x, y);
        
        ll res = 0LL;
        if(x + 1 <= y - 1) {
            res = (res + qSum(x + 1, y - 1, a[y], v[y], 1)) % P;
            res = (res + qSum(x + 1, y - 1, a[x], v[x], 0)) % P;
        }
        if(a[y] < a[x]) res = ((res + v[x]) % P + v[y]) % P;
        
        ans = (ans - res + P) % P;
        
        res = 0LL;
        if(x + 1 <= y - 1) {
            res = (res + qSum(x + 1, y - 1, a[y], v[y], 0)) % P;
            res = (res + qSum(x + 1, y - 1, a[x], v[x], 1)) % P;
        }
        
        if(a[y] > a[x]) res = ((res + v[x]) % P + v[y]) % P;
        ans = (ans + res) % P;
        
        printf("%lld
", ans);
        
        clear(x, a[x]), clear(y, a[y]);
        change(x, a[y], v[y]), change(y, a[x], v[x]);
        swap(a[x], a[y]), swap(v[x], v[y]);
    }
    
    return 0;
}

// luogu-judger-enable-o2
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
typedef long long ll;

const int N = 5e4 + 5;
const int M = 2e7 + 5;
const ll P = 1e9 + 7;

int n, m, a[N];
ll v[N], ans = 0;

namespace FhqTreap {
    int root[M], nodeCnt, ch[M][2], pri[M], siz[M];
    ll key[M], sum[M], sel[M];
    
    #define lc ch[p][0]
    #define rc ch[p][1]
    
    inline void up(int p) {
        if(p) {
            siz[p] = siz[lc] + siz[rc] + 1;
            sum[p] = (sum[lc] % P + sum[rc] % P + sel[p] % P) % P;
        }
    }
    
    inline int newnode(ll val, ll selV) {
        ++nodeCnt;
        key[nodeCnt] = val, sum[nodeCnt] = sel[nodeCnt] = selV;
        pri[nodeCnt] = rand(), siz[nodeCnt] = 1;
        return nodeCnt;
    }
    
    void split(int p, ll val, int &x, int &y) {
        if(!p) x = y = 0;
        else {
            if(val >= key[p])
                x = p, split(rc, val, rc, y);
            else 
                y = p, split(lc, val, x, lc);
            up(p);
        }
    }
    
    int merge(int x, int y) {
        if(!x || !y) return x + y;
        else {
            if(pri[x] < pri[y]) {
                ch[x][1] = merge(ch[x][1], y);
                up(x);
                return x;
            } else {
                ch[y][0] = merge(x, ch[y][0]);
                up(y);
                return y;
            }    
        }    
    }
    
    inline void insert(int rt, ll val, ll selV) {
        if(!root[rt]) {
            root[rt] = newnode(val, selV);
            return;
        }
        int x, y;
        split(root[rt], val, x, y);
        root[rt] = merge(x, merge(newnode(val, selV), y));
    }
    
    inline void remove(int rt, ll val) {
        int x, y, z;
        split(root[rt], val, x, y);
        split(x, val - 1, x, z);
        z = merge(ch[z][0], ch[z][1]);
        root[rt] = merge(merge(x, z), y);
    }
    
    inline ll ask(int rt, ll val, ll selV, int type) {
        int x, y; ll res;
        if(type) {
            split(root[rt], val, x, y);
            res = (selV * siz[x] % P + sum[x]) % P; 
        } else {
            split(root[rt], val, x, y);
            res = (selV * siz[y] % P + sum[y]) % P;
        }
        root[rt] = merge(x, y);
        return res % P;
    }
    
    void Pi(int p, int *arr) {
        if(lc) Pi(lc, arr);
        printf("%d ", arr[p]);
        if(rc) Pi(rc, arr);
    }
    
    #undef lc
    #undef rc
};

namespace SegT {
    using namespace FhqTreap;
    
    #define lc p << 1
    #define rc p << 1 | 1
    #define mid ((l + r) >> 1)
    
    void ins(int p, int l, int r, int x, ll val, ll selV) {
        insert(p, val, selV);
        if(l == r) return;
        if(x <= mid) ins(lc, l, mid, x, val, selV);
        else ins(rc, mid + 1, r, x, val, selV);
    }
    
    void del(int p, int l, int r, int x, ll val) {
        remove(p, val);
        if(l == r) return;
        if(x <= mid) del(lc, l, mid, x, val);
        else del(rc, mid + 1, r, x, val);
    }
    
    ll query(int p, int l, int r, int x, int y, ll val, ll selV, int type) {
        if(x <= l && y >= r) return ask(p, val, selV, type) % P;
        
        ll res = 0;
        if(x <= mid) res = (res + query(lc, l, mid, x, y, val, selV, type)) % P;
        if(y > mid) res = (res + query(rc, mid + 1, r, x, y, val, selV, type)) % P;
        return res;
    }
    
    void print(int p, int l, int r, int *arr) {
        Pi(root[p], arr), printf("
");
        if(l == r) return;
        print(lc, l, mid, arr), print(rc, mid + 1, r, arr);
    }
    
} using namespace SegT;

template <typename T>
inline void swap(T &x, T &y) {
    T t = x;
    x = y;
    y = t;
}

namespace IOstream{
    const int L = 1 << 15;
    
    char buffer[L], *S, *T;
    
    inline char Getchar() {
        if(S == T) {
            T = (S = buffer) + fread(buffer, 1, L, stdin);
            if(S == T) return EOF;
        }
        return *S++;
    }
    
    template <class T> 
    inline void read(T &X) {
        char ch; T op = 1;
        for(ch = Getchar(); ch > '9' || ch < '0'; ch = Getchar())
            if(ch == '-') op = -1;
        for(X = 0; ch >= '0' && ch <= '9'; ch = Getchar()) 
            X = (X << 1) + (X << 3) + ch - '0'; 
        X *= op;
    }
    
    template <typename T>
    inline void write(T x)
    {
        T sta[15]; int len = 0;
        if(x < 0) putchar('-'), x = -x;
        if(x == 0) {
            putchar('0');
            return;
        }
        for(; x > 0; sta[++len] = x % 10, x /= 10);
        for(int i = len; i >= 1; i--) putchar(sta[i] + '0');
    }
    
} using namespace IOstream;

namespace BinaryIndexTree {
    int cnt[N]; ll s[N];
    
    #define lowbit(x) (x & (-x))
    
    inline void modifyS(int p, ll val) {
        for(; p <= n; p += lowbit(p)) s[p] = (s[p] + val) % P;
    }
    
    inline void modifyC(int p) {
        for(; p <= n; p += lowbit(p)) cnt[p]++;
    }
    
    inline ll getSum(int p) {
        ll res = 0;
        for(; p > 0; p -= lowbit(p)) res = (res + s[p]) % P;
        return res;
    }
    
    inline int getCnt(int p) {
        int res = 0;
        for(; p > 0; p -= lowbit(p)) res += cnt[p];
        return res;
    }
    
} using namespace BinaryIndexTree;

int main() {
//    freopen("1.in", "r", stdin);
//    freopen("mine.out", "w", stdout);
    
//    srand(19260817);
    
    read(n), read(m);
    nodeCnt = 0;
    for(int i = 1; i <= n; i++) {
        read(a[i]), read(v[i]);
        ans = (ans + (getSum(n) - getSum(a[i]) + P) % P + P + v[i] * (getCnt(n) - getCnt(a[i])) % P + P) % P;
        modifyS(a[i], v[i]), modifyC(a[i]);
        ins(1, 1, n, i, a[i], v[i]);
    }
    
//    printf("%d
", ans);
    
    for(int x, y; m--; ) {
        read(x), read(y);
        if(x == y) {
            printf("%lld
", ans);
            continue;
        }
        if(x > y) swap(x, y);
        
        ll res = 0;
        if(x + 1 <= y - 1) {
            res = (res + query(1, 1, n, x + 1, y - 1, a[y], v[y], 0)) % P;
            res = (res + query(1, 1, n, x + 1, y - 1, a[x], v[x], 1)) % P; 
        }
        if(a[y] < a[x]) res = (res % P + v[x] % P + v[y] % P) % P;
        ans = (ans - res + P) % P;
        
        res = 0;
        if(x + 1 <= y - 1) {
            res = (res + query(1, 1, n, x + 1, y - 1, a[y], v[y], 1)) % P;
            res = (res + query(1, 1, n, x + 1, y - 1, a[x], v[x], 0)) % P; 
        }
        if(a[y] > a[x]) res = (v[y] % P + v[x] % P + res % P) % P;
        ans = (ans + res) % P;
        
        write(ans), puts("");
        
        del(1, 1, n, x, a[x]), del(1, 1, n, y, a[y]);
        ins(1, 1, n, y, a[x], v[x]), ins(1, 1, n, x, a[y], v[y]);
        swap(a[x], a[y]), swap(v[x], v[y]);
        
/*        print(1, 1, n, key), printf("
");
        print(1, 1, n, sel), printf("
");   */
    }
    
    return 0;
}