https://ctp314.github.io/2020/01/31/CF1091E-New-Year-and-the-Acquaintance-Estimation%E9%A2%98%E8%A7%A3/#more
[CF1091E]New Year and the Acquaintance Estimation题解简单无向图的可视化，根据 Erdős–Gallai 定理将度数序列 $d$ 排序可得，若满足 $$\forall k\in[1,n],\sum_{i=1}^kd_k\le k\times(k-1)+\sum_{i=k+1}^n\min(k,d_i)$$
https://ctp314.github.io/2020/01/31/CF1091E-New-Year-and-the-Acquaintance-Estimation%E9%A2%98%E8%A7%A3/#more
[CF1091E]New Year and the Acquaintance Estimation题解简单无向图的可视化，根据 Erdős–Gallai 定理将度数序列$d$ 排序可得，若满足 $$\forall k\in[1,n],\sum_{i=1}^kd_k\le k\times(k-1)+\sum_{i=k+1}^n\min(k,d_i)$$