5. Merge k Sorted Lists

merge-k-sorted-lists/sunjae95.js

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+/**
+ * @description
+ * queue의 특성을 활용하여 풀이
+ *
+ * n = length of lists
+ * m = length of lists[i]
+ * time complexity: O(n * n * m)
+ * space complexity: O(n*m)
+ */
+var mergeKLists = function (lists) {
+  let answer = null;
+  let tail = null;
+  let totalSize = lists.reduce((size, list) => {
+    let head = list;
+    let count = 0;
+
+    while (head) {
+      head = head.next;
+      count++;
+    }
+
+    return size + count;
+  }, 0);
+
+  while (totalSize--) {
+    let minIndex = lists.reduce((acc, list, i) => {
+      if (list === null) return acc;
+      if (acc === null) return { value: list.val, index: i };
+      return acc.value < list.val ? acc : { value: list.val, index: i };
+    }, null).index;
+
+    if (answer === null) {
+      answer = lists[minIndex];
+      tail = answer;
+    } else {
+      tail.next = lists[minIndex];
+      tail = lists[minIndex];
+    }
+
+    lists[minIndex] = lists[minIndex].next;
+  }
+  return answer;
+};