Hello, I'm still in high school and I have some problems trying to understand the Dijkstra's algorith. I wanted to know if someone would be so kind to show/teach me how to solve this kind of problems for high school competitions. I already understand and know how to code a BFS and a DFS, but I'm struggling with the dijkstra. I need a fast way to do it for the competitions. I use Java, but I should be able to understand other languages like c++, and c#
Dijkstra's Algorithm on HackerEarth.
CodeForces is more challenging and competitive, but if you're just starting, I suggest you try UVa online judge for lower bound programming practice. UVa online judge has good elementary problems if you're just starting to learn classical algorithms like Dijkstra. You can try these problems.
UVa 10986 — Sending Email
UVa 10389 — Subway
UVa 1112 — Mice and Maze
Also, there's an app called uHunt that tracks your progress and has lists of algorithms you ought to learn if you want to do competitive programming. Helped me a lot in high school. Of course, try challenging yourself in CodeForces and join Div 2 contests if you feel you're ready and up to the task.