# Redundant Connection II LeetCode Solution

Here, We see Redundant Connection II LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

# List of all LeetCode Solution

## Problem Statement

In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents.

The given input is a directed graph that started as a rooted tree with `n` nodes (with distinct values from `1` to `n`), with one additional directed edge added. The added edge has two different vertices chosen from `1` to `n`, and was not an edge that already existed.

The resulting graph is given as a 2D-array of `edges`. Each element of `edges` is a pair `[ui, vi]` that represents a directed edge connecting nodes `ui` and `vi`, where `ui` is a parent of child `vi`.

Return an edge that can be removed so that the resulting graph is a rooted tree of `n` nodes. If there are multiple answers, return the answer that occurs last in the given 2D-array.

Example 1:

Input: edges = [[1,2],[1,3],[2,3]]
Output: [2,3]

Example 2:

Input: edges = [[1,2],[2,3],[3,4],[4,1],[1,5]]
Output: [4,1]

## Redundant Connection II LeetCode Solution C++

``````class DisjointSet
{
int *parent;
int *treeSize;
int n;
public:
DisjointSet(int n)
{
this->n = n;
parent = new int[n];
treeSize = new int[n];

for (int i = 0; i < n; i++)
{
parent[i] = i;
treeSize[i] = 1;
}
}

int find(int x)
{
if (x < 0 || x >= this->n)
return -1;
if (x == parent[x])
return x;
int root = find(parent[x]);
parent[x] = root;
return root;
}
bool connected(int x, int y)
{
return find(x) == find(y);
}

void doUnion(int x, int y)
{
int root1 = find(x);
int root2 = find(y);
if (root1 == root2)
return;
if (this->treeSize[root1] <= this->treeSize[root2])
{
parent[root1] = root2;
this->treeSize[root2] += this->treeSize[root1];
}
else
{
parent[root2] = root1;
this->treeSize[root1] += this->treeSize[root2];
}
}
};

class Solution {
public:
vector<int> findRedundantDirectedConnection(vector<vector<int>>& edges) {
int n = 0;
for(const auto &e : edges)
{
n = max(n, e[0]);
n = max(n, e[1]);
}
DisjointSet ds(n);
vector<int> indeg(n, 0);
int maxIndeg = 0;
for(const auto &e: edges)
{
int v = e[1] - 1;
indeg[v]++;
maxIndeg = max(maxIndeg, indeg[v]);
}
if(maxIndeg == 1)
{
vector<int> res = {-1,-1};
for(const auto &e : edges)
{
int u = e[0] - 1;
int v = e[1] - 1;
if(ds.connected(u, v))
res = {u+1, v+1};
ds.doUnion(u, v);
}
return res;
}
else
{
vector<int> e1 = {-1, -1};
vector<int> e2 = {-1, -1};
for(const auto &e : edges)
{
int u = e[0] - 1;
int v = e[1] - 1;
if(indeg[v] == 2)
{
if(e1 == vector<int>({-1,-1}) )
e1 = {u,v};
else
e2 = {u,v};
}
}
for(const auto &e : edges)
{
int u = e[0] - 1;
int v = e[1] - 1;
if(e2 != vector<int>({u,v}) )
ds.doUnion(u, v);
}
if(ds.connected(e2[0], e2[1]))
return {e2[0] + 1, e2[1] + 1};
else
return {e1[0] + 1, e1[1] + 1};
}
}
};```Code language: PHP (php)```

## Redundant Connection II LeetCode Solution Java

``````class Solution {
public int[] findRedundantDirectedConnection(int[][] edges) {
int[]inDegree = new int[edges.length+1];
Arrays.fill(inDegree, -1);
int bl1 = -1, bl2 = -1;
for(int i=0; i<edges.length; i++){
int u = edges[i][0];
int v = edges[i][1];
if(inDegree[v] == -1){
inDegree[v] = i;
} else {
bl1 = i;
bl2 = inDegree[v];
break;
}
}

int[]parent = new int[edges.length+1];
int[]rank = new int[edges.length+1];
for(int i=0; i<parent.length; i++) parent[i] = i;
for(int i=0; i<edges.length; i++){
if(i == bl1) continue;
int[]edge = edges[i];
boolean bool = union(edge[0], edge[1], parent, rank);
if(bool){
if(bl1 == -1){
return edge;
} else{
return edges[bl2];
}
}
}
return edges[bl1];
}
public int find(int x, int[]parent){
if(x == parent[x]) return x;
else return find(parent[x], parent);
}

public boolean union(int s1, int s2, int[]parent, int[]rank){
} else{
}
return false;
} else return true;
}
}```Code language: PHP (php)```

## Redundant Connection II LeetCode Solution JavaScript

``````var findRedundantDirectedConnection = function (edges) {
let n = edges.length;
let parent = Array(n + 1).fill(0);
let first = second = [];
for (let edge of edges) {
if (parent[edge[1]] === 0) {
parent[edge[1]] = edge[0];
} else {
first = [parent[edge[1]], edge[1]];
second = [...edge];
edge[1] = 0;
}
}
for (let i = 0; i <= n; ++i) parent[i] = i;
for (let edge of edges) {
if (edge[1] === 0) continue;
let [x, y] = [find(parent, edge[0]), find(parent, edge[1])];
if (x === y) return first.length === 0 ? edge : first;
parent[x] = y;
}
return second;
};

function find(parent, x) {
return x === parent[x] ? x : find(parent, parent[x]);
}```Code language: PHP (php)```

## Redundant Connection II LeetCode Solution Python

``````class Solution(object):
def findRedundantDirectedConnection(self, edges):
n = len(edges)
parent = dict(zip(range(1,n+1), range(1,n+1)))
last_cycle_edge = candidate_edge = candidate = None
def root(v):
while parent[v] != v:
v = parent[v]
return v
for e in edges:
v, w = e
if parent[w] != w:
candidate_edge, candidate = e, w
continue
if root(v) == w:
last_cycle_edge = e
continue
parent[w], n = v, n-1
return [parent[candidate], candidate] if n > 1 else (candidate_edge or last_cycle_edge)``````
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