## 615 - Is It A Tree?
Difficulty : mediumSolution Description : Graph problem Here is maximum 100 pair in a input set. So, you can store parent and child in two array. parent[101], child[101]. Do not use adjacency matrix because value of a node is not small. Suppose a pair (x,y) if x==y then it is not a tree. Example 1 1 0 0. it is not a tree. If any child have more than 1 parent then it is not a tree. Example 1 2 3 2 0 0. Here node 2 have more than 1 parent so it is not a tree. Find the main root. Main root is a node which has no parent. Example 1 2 1 3 3 4 0 0. Here main root is 1 Run any graph traversal algorithm where start node main root. If all other node visited from start node then it is a tree. otherwise it is not a tree. For traversal you can use the recursion method DFS(int root) ----for i=0 to N //Here N=number of pair -------if(parent[i]==root) DFS(child[i]) Remember if a input graph is empty then it is a tree. Example 0 0. It is a tree. |
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