Inversion (hdu 4911 tree-like array | | Merge sort to reverse order)

InversionTime limit:2000/1000 MS (java/others) Memory limit:131072/131072 K (java/others)
Total submission (s): 2003 Accepted Submission (s): 787


Problem Descriptionbobo has a sequence a1,a2,...,. He is allowed to swap adjacentNumbers 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≤i<j≤n and Ai>aj.
Inputthe input consists of several tests. For each tests:

The first line contains 2 integers n,k (1≤n≤105,0≤k≤109). The second line contains n integers a1,a2,..., an (0≤ai≤109).
Outputfor each tests:

A single integer denotes the minimum number of inversions.
Sample Input

3 12 2 13 02 2 1

Sample Output

12

Authorxiaoxu Guo (Ftiasch)
Source2014 multi-university Training Contest 5
Recommendwe carefully selected several similar problems for you:5197 5196 5193 5192 5189

Test instructions: In order to find the number of n reverse logarithm, you can exchange K adjacent, so the original sequence of reverse order minus K.

Idea: There are two ways to reverse the order, merging the sort and the tree array. Several methods to find the right of reverse order

Code:

Tree-like array # include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <cmath> #include <string> #include <map> #include <stack> #include <vector> #include < set> #include <queue> #pragma comment (linker, "/stack:102400000,102400000") #define MAXN 100005#define MAXN 2005#define mod 1000000009#define INF 0x3f3f3f3f#define pi ACOs ( -1.0) #define EPS 1e-6#define Lson rt<<1,l,mid# Define Rson rt<<1|1,mid+1,r#define FRE (i,a,b) for (i = A; I <= b; i++) #define FREE (i,a,b) for (i = A; I >= B; i --) #define FRL (i,a,b) for (i = A; I < b; i++) #define FRLL (i,a,b) for (i = A; i > b; i--) #define MEM (T, v) memset (( T), V, sizeof (t)) #define SF (n) scanf ("%d", &n) #define SFF (A, b) scanf ("%d%d", &a, &b) #define SFFF (A, B,C) scanf ("%d%d%d", &a, &b, &c) #define PF printf#define DBG pf ("hi\n") typedef long LONG LL ; using namespace Std;int n,k,len;int bit[maxn];int a[maXn],num[maxn];map<int,int>pos;int cmp (int a,int b) {return a>b;} int lowbit (int i) {return i&-i;}    ll sum (int i) {ll s=0;        while (i>0) {s+=bit[i];    I-=lowbit (i); } return s;}        void Add (int i,int x) {while (I&LT;MAXN) {bit[i]+=x;    I+=lowbit (i);    }}ll solve () {int i,j;    ll Ans=0;        FRE (i,1,n) {ans+=sum (pos[num[i]]-1);    Add (pos[num[i]],1);    } ans-=k;    if (ans<0) ans=0; return ans;}    int main () {int i,j;        while (~SFF (n,k)) {pos.clear ();        MEM (bit,0);            FRE (i,1,n) {SF (a[i]);        Num[i]=a[i];        } sort (a+1,a+n+1,cmp);        Len=1;        Pos[a[1]]=len;        FRE (i,2,n)//map de-weight, discretized if (a[i]!=a[i-1]) Pos[a[i]]=++len;        PF ("len=%d\n", Len);    PF ("%i64d\n", Solve ()); } return 0;}

Merge sort # include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <cmath> #include <string> #include <map> #include <stack> #include <vector> #include < set> #include <queue> #pragma comment (linker, "/stack:102400000,102400000") #define MAXN 100005#define MAXN 2005#define mod 1000000009#define INF 0x3f3f3f3f#define pi ACOs ( -1.0) #define EPS 1e-6#define Lson rt<<1,l,mid# Define Rson rt<<1|1,mid+1,r#define FRE (i,a,b) for (i = A; I <= b; i++) #define FREE (i,a,b) for (i = A; I >= B; i --) #define FRL (i,a,b) for (i = A; I < b; i++) #define FRLL (i,a,b) for (i = A; i > b; i--) #define MEM (T, v) memset (( T), V, sizeof (t)) #define SF (n) scanf ("%d", &n) #define SFF (A, b) scanf ("%d%d", &a, &b) #define SFFF (A, B,C) scanf ("%d%d%d", &a, &b, &c) #define PF printf#define DBG pf ("hi\n") typedef long LONG LL ; using namespace Std;int a[maxn];int N,k;__int64 ans;voID Merge (int a[],int l,int mid,int r) {int i,j,k=l;    int *b=new int[r+1];    FRE (I,l,r) b[i]=a[i];    i=l,j=mid+1;        while (i<=mid&&j<=r) {if (B[i]<=b[j]) a[k++]=b[i++];            else{a[k++]=b[j++];        ans+= (mid-i+1);    }} while (I<=mid) a[k++]=b[i++];    while (J&LT;=R) a[k++]=b[j++]; delete []b;}    void Merge_sort (int a[],int l,int R) {if (l==r) return;    int mid= (L+R) >>1;    Merge_sort (A,l,mid);    Merge_sort (A,MID+1,R); Merge (a,l,mid,r);}    int main () {int i,j;        while (~SFF (n,k)) {FRE (i,1,n) SF (A[i]);        ans=0;        Merge_sort (A,1,n);        Ans-=k;        if (ans<0) ans=0;    PF ("%i64d\n", ans); } return 0;}

Inversion (hdu 4911 tree-like array | | Merge sort to reverse order)