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Language: Default Ultra-QuickSort
Description
9 1 0 5 4 , Ultra-QuickSort produces the output 0 1 4 5 9 . Your task is to determine how many swap operations Ultra-QuickSort needs to perform in order to sort a given input sequence. Input The input contains several test cases. Every test case begins with a line that contains a single integer n < 500,000 -- the length of the input sequence. Each of the the following n lines contains a single integer 0 ≤ a[i] ≤ 999,999,999, the i-th input sequence Output For every input sequence, your program prints a single line containing an integer number op, the minimum number of swap operations necessary to sort the given input sequence. Sample Input 5 9 1 0 5 4 3 1 2 3 0 Sample Output 6 0 Source |
In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is题意：求n个数的逆序对。
代码：
归并排序：
#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 501005
#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;
ll a[maxn];
ll b[maxn];
ll n,ans;
void Merge(ll a[],ll l,ll mid,ll r)
{
int i,j,k=l;
// int *b=new int[r+1]; //不要动态申请，会超时的
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<=r) a[k++]=b[j++];
// delete []b;
}
void Merge_sort(ll a[],ll l,ll r)
{
if (l>=r) return ;
ll 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 (scanf("%lld",&n),n)
{
ans=0;
FRE(i,1,n)
scanf("%lld",&a[i]);
Merge_sort(a,1,n);
pf("%lld\n",ans);
}
return 0;
}
树状数组：
#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 501005
#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 __int64 ll;
using namespace std;
struct Node
{
int val;
int pos;
}node[maxn];
int n;
ll ans;
int bit[maxn];
int cmp(Node a,Node b)
{
return a.val>b.val;
}
ll sum(int i)
{
ll s=0;
while (i>0)
{
s+=bit[i];
i-=i&-i;
}
return s;
}
void add(int i,int x)
{
while (i<=n)
{
bit[i]+=x;
i+=i&-i;
}
}
int main()
{
int i,j;
while (scanf("%d",&n),n)
{
FRE(i,0,n+10) bit[i]=0;
FRE(i,1,n)
{
scanf("%d",&node[i].val);
node[i].val;
node[i].pos=i;
}
sort(node+1,node+n+1,cmp);
ans=0;
FRE(i,1,n)
{
ans+=sum(node[i].pos-1);
add(node[i].pos,1);
}
pf("%I64d\n",ans);
}
return 0;
}