本文共 954 字，大约阅读时间需要 3 分钟。

#include
   
    #include
    
     typedef __int64 LL;const LL M = 100005;LL a[M],c[M];LL n;LL lowbit(LL x){    return x&(-x);}void add(LL pos,LL x){    LL num = pos;    while(pos <= n)    {        a[pos] += num;        c[pos] += x;        pos += lowbit(pos);    }}LL get_sum1(LL pos){    LL res = 0;    while(pos > 0)    {        res += c[pos];        pos -= lowbit(pos);    }    return res;}LL get_sum2(LL pos){    LL res = 0;    while(pos > 0)    {        res += a[pos];        pos -= lowbit(pos);    }    return res;}int main(){    LL m,x,ret,k;    while(~scanf("%I64d",&n))    {        LL ret = 0;        memset(a,0,sizeof(a));        memset(c,0,sizeof(c));        for(LL i = 1;i <= n;i++)        {            scanf("%I64d",&m);            add(m,1);            x = i - get_sum1(m);            if(x)            {                 k = get_sum2(n) - get_sum2(m);                 ret += x * m + k;            }        }        printf("%I64d\n",ret);    }}
    
   

转载地址：http://aysgi.baihongyu.com/