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）
1 #include <cstdio> 2 #include <string> 3 #include <iostream> 4 #include <algorithm> 5 #include <cmath> 6 #include <cstring> 7 #include <complex> 8 #include <set> 9 #include <vector> 10 #include <map> 11 #include <queue> 12 #include <deque> 13 #include <ctime> 14 15 using namespace std; 16 17 const double EPS = 1e-8; 18 19 #define ABS(x) ((x)<0?(-(x)):(x)) 20 #define SQR(x) ((x)*(x)) 21 #define MIN(a,b) ((a)<(b)?(a):(b)) 22 #define MAX(a,b) ((a)>(b)?(a):(b)) 23 24 #define LSON(x) ((x)<<1) 25 #define RSON(x) (((x)<<1)+1) 26 #define LOWBIT(x) ((x)&(-(x))) 27 #define MAXS 1111 28 #define MAXN 222222 29 #define VOIDPOINT 0 30 #define LL long long 31 #define OO 214748364 32 33 struct TreeArray{ 34 int tree[MAXN], n; 35 int f[MAXN]; 36 void clear(int nn = MAXN - 20) { 37 n = nn; 38 memset(tree, 0, sizeof(tree[0])*(n+10)); 39 memset(f, 0, sizeof(f[0])*(n+10)); 40 } 41 void add(int x, int num = 1) { 42 if (x < 1) puts("Error in TreeArray, x must > 0!!"); 43 f[x] += num; 44 while (x <= n) { 45 tree[x] += num; 46 x += LOWBIT(x); 47 } 48 } 49 int get(int x) { 50 int res = 0; 51 while (x > 0) { 52 res += tree[x]; 53 x -= LOWBIT(x); 54 } 55 return res; 56 } 57 int getright(int x) { // get [x ~ n] 58 return get(n) - get(x-1); 59 } 60 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 61 int res = 0, sum = 0; 62 sum = get(x); 63 while (sum) { 64 if (sum == k && f[x]) { 65 res = x; break; 66 } 67 if (sum - tree[x] >= k) { 68 sum -= tree[x]; 69 x -= LOWBIT(x); 70 } else { 71 if (f[x]) sum -= f[x]; 72 --x; 73 } 74 } 75 add(res, -1); 76 return res; 77 } 78 } TreeL, TreeR; 79 80 int a[MAXN]; 81 vector <int > lsh; 82 LL ans, n, k; 83 84 void init() { 85 lsh.clear(); 86 for (int i = 0; i < n; ++i) { 87 scanf("%d", a+i); 88 lsh.push_back(a[i]); 89 } 90 sort(lsh.begin(), lsh.end()); 91 lsh.erase(unique(lsh.begin(), lsh.end()), lsh.end()); 92 for (int i = 0; i < n; ++i) a[i] = lower_bound(lsh.begin(), lsh.end(), a[i]) - lsh.begin() + 1; 93 } 94 95 void solve() { 96 ans = 0; 97 int sum = 0, head = 0, tail = n; 98 TreeL.clear(n); TreeR.clear(n); 99 TreeL.add(a[0]); 100 while (head + 1 < tail && \ 101 sum + TreeL.getright(a[tail-1]+1) + TreeR.get(a[tail-1]-1) <= k) { 102 sum += TreeL.getright(a[tail-1]+1) + TreeR.get(a[tail-1]-1); 103 --tail; 104 TreeR.add(a[tail]); 105 } 106 107 ans += n - tail; 108 109 110 for (head = 1; head < n; ++head) { 111 if (head == tail) { 112 sum -= (TreeL.getright(a[tail]+1) + TreeR.get(a[tail]-1)); 113 TreeR.add(a[tail++], -1); 114 } 115 TreeL.add(a[head]); 116 sum += TreeL.getright(a[head]+1) + TreeR.get(a[head]-1); 117 while (sum > k && tail < n) { 118 sum -= TreeL.getright(a[tail]+1) + TreeR.get(a[tail]-1); 119 TreeR.add(a[tail++], -1); 120 } 121 ans += n - tail; 122 } 123 } 124 125 int main() { 126 // freopen("test.txt", "r", stdin); 127 while (cin >> n >> k) { 128 init(); 129 solve(); 130 cout << ans << endl; 131 } 132 return 0; 133 }
