|
| 1 | +function ListNode(val, next) { |
| 2 | + this.val = val === undefined ? 0 : val; |
| 3 | + this.next = next === undefined ? null : next; |
| 4 | +} |
| 5 | + |
| 6 | +/** |
| 7 | + * @param {ListNode} list1 |
| 8 | + * @param {ListNode} list2 |
| 9 | + * @return {ListNode} |
| 10 | + */ |
| 11 | +var mergeTwoLists = function (list1, list2) { |
| 12 | + if (!list1 && !list2) { |
| 13 | + return null; |
| 14 | + } |
| 15 | + |
| 16 | + if (!list1 || !list2) { |
| 17 | + return [list1, list2].find(Boolean); |
| 18 | + } |
| 19 | + |
| 20 | + // firstPointer is a head of list who has the smallest value of node |
| 21 | + let [firstPointer, secondPointer] = |
| 22 | + list1.val < list2.val ? [list1, list2] : [list2, list1]; |
| 23 | + const mergedList = firstPointer; |
| 24 | + |
| 25 | + if (firstPointer.next === null) { |
| 26 | + firstPointer.next = secondPointer; |
| 27 | + return mergedList; |
| 28 | + } |
| 29 | + |
| 30 | + while (secondPointer !== null) { |
| 31 | + let nextFirstPointer = firstPointer.next; |
| 32 | + const nextSecondPointer = secondPointer.next; |
| 33 | + |
| 34 | + while ( |
| 35 | + firstPointer.next !== null && |
| 36 | + firstPointer.next.val < secondPointer?.val |
| 37 | + ) { |
| 38 | + firstPointer = firstPointer.next; |
| 39 | + nextFirstPointer = firstPointer.next; |
| 40 | + } |
| 41 | + |
| 42 | + firstPointer.next = secondPointer; |
| 43 | + firstPointer.next.next = nextFirstPointer; |
| 44 | + |
| 45 | + secondPointer = nextSecondPointer; |
| 46 | + firstPointer = firstPointer.next; |
| 47 | + } |
| 48 | + |
| 49 | + return mergedList; |
| 50 | +}; |
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