poj 2299 又是逆序数。。。

这个要先离散化。。。然后还是树状数组求。。。。 #include<cstdio>#include<stdlib h="">#include<string h="">#include<string>#include<cmath>#include<cstring>#include#include<map>#include<set>#include<queue>#include<vector>using namespace std;typedef long long ll;int bit[500005],k[500005];int n;struct node{ int x; int p;}a[500005];bool cmp(const node& a1,const node& a2){ return a1.x0) { s+=bit[i]; i-=i&-i; } return s;}void add(int i,int x){ while(i<=n) { bit[i]+=x; i+=i&-i; }}ll solve(){ ll ans=0; for(int j=1;j<=n;j++) { ans+=j-1-sum(k[j]); add(k[j],1); } return ans;}int main(){//freopen("in.txt","r",stdin);//freopen("out.txt","w",stdout); while(scanf("%d",&n)!=EOF){ if(n==0) break; memset(k,0,sizeof(k)); memset(bit,0,sizeof(k)); for(int i=1;i<=n;i++) { scanf("%d",&a[i].x); a[i].p=i; } sort(a+1,a+n+1,cmp); for(int i=1;i<=n;i++) { k[a[i].p]=i; } // for(int i=1;i<=n;i++) // printf("%d ",k[i]); printf("%lld\n",solve()); }return 0;}</a2></vector></queue></set></map></algorithm></cstring></cmath></string></string></stdlib></cstdio>