1
var minReorder = function (n, connections) {
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  // from: (<from city>, [<to cities>])
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  // to: (<to city>, [<from cities>])
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  const from = new Map(),
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    to = new Map();
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  // Function to insert in values in map
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  const insert = (map, key, value) => {
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    if (map.has(key)) {
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      const arr = map.get(key);
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      arr.push(value);
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      map.set(key, arr);
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    } else {
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      map.set(key, [value]);
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    }
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  };
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  // Set all values in both maps
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  for (const [a, b] of connections) {
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    insert(from, a, b);
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    insert(to, b, a);
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  }
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  // Queue: cities to visit
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  const queue = [0],
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    visited = new Set();
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  let count = 0;
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  while (queue.length) {
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    const cur = queue.shift(); // First element in queue
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    // Check values in first map
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    if (from.has(cur)) {
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      for (const x of from.get(cur)) {
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        // If visited, do nothing else add to queue
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        if (visited.has(x)) continue;
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        queue.push(x);
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        count++; // Change direction of this path
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      }
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    }
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    if (to.has(cur)) {
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      // If visited, do nothing else add to queue
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      for (const x of to.get(cur)) {
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        if (visited.has(x)) continue;
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        queue.push(x);
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      }
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    }
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    visited.add(cur); // Mark city as visited
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  }
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  return count;
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};