hdu 2227

和之前的hdu3030都快一样了

可以参考之前的题解

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 1e5+5;
long long n;
long long a[maxn];
long long b[maxn];
long long c[maxn];
long long mod = 1e9+7;
void add(long long c[],long long i,long long j);
long long getsum(long long c[],long long i);
int main()
{
    int i,j,k;
    while(scanf("%lld",&n) != EOF)
    {
        memset(c, 0, sizeof(c));
        for(i=1;i<=n;++i)
        {
            scanf("%lld",a+i);
            b[i] = a[i];
        }
        sort(b+1,b+n+1);
        long long sum = 0;
        for(i=1;i<=n;++i)
        {
            long long ans=0;
            long long pos=lower_bound(b+1,b+n+1,a[i]) - b;
            ans = getsum(c,pos);
            sum += ans+1;
            sum %= mod;
            add(c, pos, ans+1);
        }
        printf("%lld
",sum);
    }
}
long long lowbit(long long k)
{
    return k&(-k);
}
void add(long long c[],long long i,long long j)
{
    while(i<=n)
    {
        c[i] += j;
        c[i] %= mod;
        i += lowbit(i);
    }
}
long long getsum(long long c[],long long i)
{
    long long sum = 0;
    while(i > 0)
    {
        sum += c[i];
        sum %= mod;
        i -= lowbit(i);
    }
    return sum;
}