Spoj Minimum Spanning Tree

#1

Why am i getting 90,91 score ,Why not 100
This is my code.

#2

Do the following in union:
a = find_set(a);
b = find_set(b);
if (a != b) {
if (rank[a] < rank[b])
swap(a, b);
parent[b] = a;
if (rank[a] == rank[b])
rank[a]++;
}

#3

What difference will it cause in terms of Time Complexity??

#4

Using rank in merging is faster than directly merging. Sometimes it become constant too. But at max it is of O(logn)

#5

I have also used rank in merging