摘要:
hoj2275:http://acm.hit.edu.cn/hoj/problem/view?id=2275题意:给一个数列,问有多少组满足:三个数Ai < Aj > Ak 且 i < j < k.解法:树状数组:用数组left存储所有比左边的数小的数的个数,则结果为left值*(所有比右边的数小的数的个数)code:#include<iostream>#include<cstdlib>#include<cstdio>int num[50010],c[50010],left[50010];long long s;int lowbit( 阅读全文