hdu 6090

思路：菊花状的图。。。注意边大于构成完全图的情况

 1 #include<bits/stdc++.h>
 2 typedef long long ll;
 3 using namespace std;
 4
 5 int main(){
 6     int t;
 7     scanf("%d",&t);
 8     while(t--){
 9         ll n,m;
10         scanf("%lld%lld",&n,&m);
11         ll sum=0;
12         if(m>=n-1){
13             sum+=n-1;
14             sum+=(n-1)*(1+(n-2)*2);
15             m-=n-1;
16             if(m>0){
17                 sum-=min(m,n-1)*2;
18                 m-=n-1;
19             }
20             for(ll i=n-3;i>=1;i--){
21                 if(m<=0) break;
22                 sum-=min(m,i)*2;
23                 m-=i;
24             }
25             sum=max(sum,n*(n-1));
26         }
27         else {
28             ll x=n-(m+1);
29             sum+=m;
30             sum+=m*(1+(m-1)*2);
31             sum+=2*x*(m+1)*n;
32             sum+=(n-m-1)*(n-m-2)*n;
33         }
34         printf("%lld\n",sum);
35     }
36 }