折戟沉沙

John has n tasks to do. Unfortunately, the tasks are not independent and the execution of one task is only possible if other tasks have already been executed. Input The input will consist of s

三道题基本一样 裸的拓扑排序,判环;也可以赋值负权加dfs-spfa判#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fod(i,a,b) for(int i=a;i>=