To know the number of compatible pairs of warehouses in the given tree network, follow these steps:
1. Preprocessing: Calculate the shortest path distances from root (warehouse 1) to all other nodes using Dijkstra's algorithm or Floyd-Warshall algorithm.
2. Recursively traverse the tree from the root node. For each node u, keep track of the total number of compatible pairs (count).
a. Check Children: Recursively visit each child node v of u.
- Compatibility Check: If u is an ancestor of v and distance(u, v) ≤ val[v], then the pair (u, v) is compatible. Increment count by 1.
b. Add Ancestors: Add u to the list of ancestors for all its children. This will ensure that compatible pairs involving u are counted when traversing its descendants.
3. Lastly, Post-processing: After traversing the entire tree, the total count will represent the number of compatible pairs of warehouses.
See text structure:
Compatible Warehouses:
HackerLand has a network of warehouses which can be represented as an undirected rooted weighted tree consisting of warehouse_nodes number of nodes, rooted at warehouse 1. There are (warehouse_nodes - 1) roads connecting them, and warehouse_weight[i] denotes the distance covered by the ith road. Moreover, each warehouse has a value assigned to it denoted by the array val.
A pair of warehouses (u, v) is said to be compatible if it satisfies the following conditions:
• u is an ancestor of v in the tree network.
• distance(u, v) ≤ val[v], where distance(u, v) represents the sum of distances of roads that belong to the simple path connecting u and v.