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Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 5081 Accepted Submission(s): 1871
#include <iostream> #include <stdio.h> #include <string.h> #include <stack> #include <vector> #include <algorithm> using namespace std; const int N = 100005; int n,c[N],L[N],a[N]; int lowbit(int x){ return x&(-x); } void update(int idx,int v){ for(int i=idx;i<=N;i+=lowbit(i)){ c[i]+=v; } } int getsum(int idx){ int sum = 0; for(int i=idx;i>=1;i-=lowbit(i)){ sum+=c[i]; } return sum; } int main() { int tcase; scanf("%d",&tcase); while(tcase--){ scanf("%d",&n); long long cnt = 0; memset(c,0,sizeof(c)); for(int i=1;i<=n;i++){ scanf("%d",&a[i]); update(a[i],1); L[i] = getsum(a[i]-1); // printf("%d\n",L[i]); } memset(c,0,sizeof(c)); for(int i=n;i>=1;i--){ update(a[i],1); int y = getsum(a[i]-1); // printf("%d\n",y); cnt+= L[i]*(n-i-y)+y*(i-L[i]-1); } printf("%lld\n",cnt); } return 0; }
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原文地址:http://www.cnblogs.com/liyinggang/p/5655999.html