存题（图的相关判断和两道精品dijkstra）

图的判断：

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805351814119424

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805349851185152

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805343979159552

https://pintia.cn/problem-sets/994805342720868352/exam/problems/1038430013544464384

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805343043829760

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805346428633088

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805347523346432

两道精品dijkstra:

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805489282433024

https://pintia.cn/problem-sets/994805342720868352/exam/problems/994805358663417856