HDOJ-2838 Cow Sorting

来源：互联网发布：windows文件夹编辑：程序博客网时间：2024/06/05 05:28

一道逆序数的题。要用两个树状数组来维护，一个记录牛的数目，另一个记录牛的脾气值.一定要注意数据溢出.

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <string>using namespace std;typedef long long LL;#define maxn 100005 int c[maxn], n;LL num[maxn];void Update(LL m){    int h = m;    while(m <= n){        num[m] += h;          c[m] += 1;        m += m & -m;    }}int Query(int m, LL &p){    int sum = 0;    while(m){        p += num[m];        sum += c[m];        m -= m & -m;     }    return sum;}int main(){//  freopen("in.txt", "r", stdin);    while(cin >> n){        memset(c, 0, sizeof(c));        memset(num, 0, sizeof(num));        LL s = 0, sum = 0;        for(int i = 1; i <= n; i++){            LL a,  p = 0;            cin >> a;            s += a;            Update(a);            sum += (i - Query(a, p))*a + s - p;        }        cout << sum << endl;    }    return 0;}

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