想了想树套树比较难写，于是块链试一下，2秒左右过了。
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdio> 5 #include <cmath> 6 using namespace std; 7 8 typedef long long ll; 9 const int INF = 9999999; 10 const int N = 200001; 11 const int M = 1000; 12 int b[M][M]; 13 int sz[M]; 14 int a[N]; 15 int d[N]; 16 int n, m, ps, k; 17 18 void remove( int num ) 19 { 20 int pos = d[num]; 21 int cur = pos / ps; 22 int w = lower_bound( b[cur], b[cur] + sz[cur], num ) - b[cur]; 23 for ( int i = w; i < sz[cur] - 1; i++ ) 24 { 25 b[cur][i] = b[cur][i + 1]; 26 } 27 sz[cur]--; 28 a[d[num]] = INF; 29 } 30 31 int query( int num ) 32 { 33 int pos = d[num]; 34 int cur = pos / ps; 35 int s = 0, c = 0; 36 for ( int i = 0; i < cur; i++ ) 37 { 38 if ( sz[i] ) 39 { 40 s += sz[i]; 41 c += upper_bound( b[i], b[i] + sz[i], num ) - b[i]; 42 } 43 } 44 for ( int i = cur * ps; i < pos; i++ ) 45 { 46 if ( a[i] != INF ) 47 { 48 s++; 49 if ( a[i] < num ) c++; 50 } 51 } 52 s -= c; 53 for ( int i = cur + 1; i < k; i++ ) 54 { 55 if ( sz[i] ) 56 { 57 s += upper_bound( b[i], b[i] + sz[i], num ) - b[i]; 58 } 59 } 60 int bound = min( n, ( cur + 1 ) * ps ); 61 for ( int i = pos + 1; i < bound; i++ ) 62 { 63 if ( a[i] < num ) 64 { 65 s++; 66 } 67 } 68 return s; 69 } 70 71 int main () 72 { 73 while ( scanf("%d%d", &n, &m) != EOF ) 74 { 75 ps = 800; 76 for ( int i = 0; i < n; i++ ) 77 { 78 scanf("%d", &a[i]); 79 b[i / ps][i % ps] = a[i]; 80 d[a[i]] = i; 81 } 82 k = ( n + ps - 1 ) / ps; 83 for ( int i = 0; i < k - 1; i++ ) 84 { 85 sz[i] = ps; 86 sort( b[i], b[i] + sz[i] ); 87 } 88 sz[k - 1] = n - ( k - 1 ) * ps; 89 sort( b[k - 1], b[k - 1] + sz[k - 1] ); 90 ll ans = 0; 91 for ( int i = 1; i <= n; i++ ) 92 { 93 ans += query(i); 94 } 95 ans = ans / 2; 96 for ( int i = 0; i < m; i++ ) 97 { 98 printf("%lld ", ans); 99 int tmp; 100 scanf("%d", &tmp); 101 ans -= query(tmp); 102 remove(tmp); 103 } 104 } 105 return 0; 106 }