HDU 4911 Inversion（求逆序對）

bobo has a sequence a 

1,a 

2,…,a 

n. he is allowed to swap twoadjacentnumbers for no more than k times. 

find the minimum number of inversions after his swaps. 

note: the number of inversions is the number of pair (i,j) where 1≤ii>a

j.input

the input consists of several tests. for each tests: 

the first line contains 2 integers n,k (1≤n≤10 

5,0≤k≤10 

9). the second line contains n integers a 

1,a 

2,…,a 

n (0≤a 

i≤10 

9).output

for each tests: 

a single integer denotes the minimum number of inversions.

sample input

3 1

2 2 1
3 02 2 1

sample output

1

2

題解：題意：

給你n個數，允許相鄰的交換k次，問你能得到的最小逆序對數

思路：一開始想用樹狀陣列來求逆序對。。後來發現1e9就放棄了。。老老實實歸併排序吧，max(逆序對數減去交換次數,0)就是答案，注意要long long

**：#include#include#include#include#include#include#include#include#include#include#include#includeusing namespace std;

#define inf 100861111

#define ll long long

#define eps 1e-15

int a[100005];

int t[100005];

ll ans;

void merge(int l,int r,int mid)

else

k++;

}while(i<=mid)

while(j<=r)

for(i=l;i<=r;i++)

a[i]=t[i];

}void guibin(int l,int r)

{ if(l

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