KYOCERA Programming Contest 2021（AtCoder Beginner Contest 200） C - Ringo‘s Favorite Numbers 2

总结:

下次组合数 只用求那种 C[2,n]这种 不需要用板子

code:

#include 
using namespace std;
typedef unsigned long long LL;
map mp;
int n;
const int N1 = 2e5+10;
int a[N1];
inline void read(int &sum)
{
    char ch = getchar();
    int tf = 0;
    sum = 0;
    while((ch  '9') && (ch != '-')) ch = getchar();
    tf = ((ch == '-') && (ch = getchar()));
    while(ch >= '0' && ch >n;
    for(int i=1; isecond >=2)
        sum+=((it->second*(it->second-1))/2);
    }
    
    cout