Teads Sponsored Contest - Solution

teads.js

var graph = [];
var n = parseInt(readline()); // the number of adjacency relations
for (var i = 0; i < n; i++) {
    var inputs = readline().split(' ');
    var xi = parseInt(inputs[0]); // the ID of a person which is adjacent to yi
    var yi = parseInt(inputs[1]); // the ID of a person which is adjacent to xi
    if (!graph[xi]) {
        graph[xi] = { data: xi, edges: [] };
    }
    graph[xi].edges.push(yi);
    if (!graph[yi]) {
        graph[yi] = { data: yi, edges: [] };
    }
    graph[yi].edges.push(xi);
    
    //printErr(xi+' <---> '+yi);
}

var max_depth = 0;

function deeepth() {
    graph.map(function(x){
        if(x.depth > max_depth) {
            max_depth = x.depth;
        } 
        if (x.depth == max_depth) {
           xi = x.data;
        }
    });
    return max_depth;
}

function explore_graph() {
    graph.map(function(x){
        x.explored  = false;
        x.pred = -1;
        x.depth = Number.MAX_VALUE;
    });
}

function bfs(n) {
    explore_graph();
    var q = [];
    graph[n].explored = true;
    graph[n].depth = 0;
    q.push(n);  
    var x = null;
    while(q.length !== 0) {
        x = q.splice(0,1)[0];  
        for(var i = 0; i < graph[x].edges.length; i++) {
           if (graph[graph[x].edges[i]].explored === false) {
                graph[graph[x].edges[i]].explored = true;
                graph[graph[x].edges[i]].pred = x;
                graph[graph[x].edges[i]].depth = graph[x].depth + 1;
                q.push(graph[x].edges[i]);
            }
        }
    }
    deeepth();
}

bfs(xi);
bfs(xi);
print(Math.ceil(max_depth / 2));