Leetcode•Jun 14, 2025
Redundant Connection
Hazrat Ali
Leetcode
You are given a graph that started as a tree with n nodes labeled from 1 to n, with one additional edge added. The added edge has two different vertices chosen from 1 to n, and was not an edge that already existed. The graph is represented as an array edges of length n where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the graph.
Return an edge that can be removed so that the resulting graph is a tree of n nodes. If there are multiple answers, return the answer that occurs last in the input.
Example 1:
Input: edges = [[1,2],[1,3],[2,3]] Output: [2,3]
Example 2:
Input: edges = [[1,2],[2,3],[3,4],[1,4],[1,5]] Output: [1,4]
Solution
/**
* @param {number[][]} edges
* @return {number[]}
*/
const findRedundantConnection = edges => {
const nums = Array(2000).fill(-1);
const find = i => {
if (nums[i] === -1) {
return i;
}
return find(nums[i]);
};
for (let i = 0; i < edges.length; i++) {
const edge = edges[i];
// Find
const x = find(edge[0]);
const y = find(edge[1]);
if (x === y) {
return edge;
}
// Union
nums[x] = y;
}
return [];
};