[DFS]

// edge
var A = Array.from({length: vertex+1}, () => []);
for (var [x,y] of arr) {
    A[x].push(y);
}

// DFS
var visited = Array.from({length: vertex+1}, () => false);
function dfs(v) {
    console.log(v);
    visited[v] = true;
    for (var x of A[v]) {
        if (!visited[x]) {
            dfs(x);
        }
    }
}

var cnt = 0;
for (var i=1; i<=vertex; i++) {
    if (!visited[i]) {
        cnt++;
        dfs(i);
    }
}