# Hard

- [Prim’s Algorithm](/algorithm-problems/algoexpert/hard/prims-algorithm.md)
- [Dijkstra’s Algorithm](/algorithm-problems/algoexpert/hard/dijkstras-algorithm.md)
- [Kruskal’s algorithm vs Prim’s algorithm](/algorithm-problems/algoexpert/hard/kruskals-algorithm-vs-prims-algorithm.md)
- [Topological Sort](/algorithm-problems/algoexpert/hard/topological-sort.md)
- [Max Sum Increasing Subsequence](/algorithm-problems/algoexpert/hard/max-sum-increasing-subsequence.md)
- [Find Nodes Distance K](/algorithm-problems/algoexpert/hard/find-nodes-distance-k.md)
- [Max Path Sum In Binary Tree](/algorithm-problems/algoexpert/hard/max-path-sum-in-binary-tree.md)
- [Validate Three Nodes](/algorithm-problems/algoexpert/hard/validate-three-nodes.md)
- [Same BST ?](/algorithm-problems/algoexpert/hard/same-bst.md)
- [Zigzag Traverse](/algorithm-problems/algoexpert/hard/zigzag-traverse.md)
- [Min Rewards](/algorithm-problems/algoexpert/hard/min-rewards.md)
- [Largest Range](/algorithm-problems/algoexpert/hard/largest-range.md)
- [Subarray Sort](/algorithm-problems/algoexpert/hard/subarray-sort.md)
- [Four Number Sum](/algorithm-problems/algoexpert/hard/four-number-sum.md)