poj 2299 Ultra-QuickSort(线段树/树状数组/归并 求逆序对)

Problem: 2299		User: shu_dayang
Memory: 7380K		Time: 500MS
Language: C++		Result: Accepted
Source Code
//树状数组
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
typedef long long LL;
#define MAXN  500005
#define MID(l,r) ((l + r) >> 1)
using namespace std;

int c[MAXN],aa[MAXN];
int n;

struct Node
{
    int val;
    int order;
}a[MAXN];

bool cmp(Node a, Node b)
{
    return a.val < b.val;
}

int lowbit(int x)
{
    return x &(-x);
}

void update(int x)
{
    while(x <= n)
    {
        c[x] += 1;
        x += lowbit(x);
    }
}

int query(int x)
{
    int sum = 0;
    while(x > 0)
    {
        sum += c[x];
        x -= lowbit(x);
    }
    return sum;
}

int main()
{
    LL ans;
    while(~scanf("%d",&n) && n != 0)
    {
        memset(c,0,sizeof(c));
        for(int i = 1; i <= n; i++)
        {
            scanf("%d",&a[i].val);
            a[i].order = i;
        }
        sort(a+1,a+1+n,cmp);
        for(int i = 1; i <= n; i++)
            aa[a[i].order] = i;

        ans = 0;
        for(int i = 1; i <= n; i++)
        {
            update(aa[i]);
            ans += i - query(aa[i]);
        }
        printf("%I64d\n",ans);
    }
    return 0;
}

 线段树：

Problem: 2299		User: shu_dayang
Memory: 9540K		Time: 922MS
Language: C++		Result: Accepted
//线段树
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
typedef long long LL;
#define MAXN  500005
#define MID(l,r) ((l + r) >> 1)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;

int sum[MAXN << 2],aa[MAXN];
int n;

struct Node
{
    int val;
    int order;
}a[MAXN];

bool cmp(Node a, Node b)
{
    return a.val < b.val;
}

void PushUp(int rt)
{
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}

void Build(int l,int r ,int rt)
{
    sum[rt] = 0;
    if(l == r)
    {
        return;
    }
    int m = MID(l,r);
    Build(lson);
    Build(rson);
}

void Update(int p,int l,int r,int rt)
{
    if(l == r)
    {
        sum[rt]++;
        return;
    }
    int m = MID(l,r);
    if(p <= m)
        Update(p,lson);
    else
        Update(p,rson);
    PushUp(rt);
}

int Query(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r <=R)
    {
        return sum[rt];
    }
    int res = 0;
    int m = MID(l,r);
    if(L<=m)
        res += Query(L,R,lson);
    if(R>m)
        res+=Query(L,R,rson);
    return res;
}

int main()
{
    LL ans;
    while(~scanf("%d",&n) && n != 0)
    {
        Build(1,n,1);
        for(int i = 1; i <= n; i++)
        {
            scanf("%d",&a[i].val);
            a[i].order = i;
        }
        sort(a+1,a+1+n,cmp);
        for(int i = 1; i <= n; i++)
            aa[a[i].order] = i;

        ans = 0;
        for(int i = 1; i <= n; i++)
        {
            Update(aa[i],1,n,1);
            ans += i - Query(1,aa[i],1,n,1);
        }
        printf("%I64d\n",ans);
    }
    return 0;
}

 归并：

Problem: 2299		User: shu_dayang
Memory: 3712K		Time: 1360MS
Language: C++		Result: Accepted
//归并
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define MID(l,r) ((l+r) >> 1)
typedef long long LL;
#define MAXN  500005
using namespace std;

int num[MAXN];
LL ans;

void Merge(int low,int mid,int high)
{
    int *temp = new int[high - low + 1];
    int k = 0;
    int i = low,j = mid + 1;
    while(i <= mid && j <= high)
    {
        if(num[i] > num[j])
        {
            ans += mid - i + 1;
            temp[k++] = num[j++];
        }
        else
        {
            temp[k++] = num[i++];
        }
    }
    while(i<=mid)    temp[k++] = num[i++];
    while(j <= high)   temp[k++] = num[j++];

    for(int i = 0; i< k; i++)
        num[low+i] = temp[i];
    delete []temp;
}

void MergeSort(int low,int high)
{
    if(low < high)
    {
        int m = MID(low,high);
        MergeSort(low,m);
        MergeSort(m+1,high);
        Merge(low,m,high);
    }
}

int main()
{
    int n;
    while(~scanf("%d",&n) && n != 0)
    {
        ans = 0;
        for(int i = 0; i< n; i++)
            scanf("%d",&num[i]);
        MergeSort(0,n-1);
        printf("%I64d\n",ans);
    }
    return 0;
}