|
617 | 617 | "This solution has only one loop, and with the `get()` method being $O(1),ドル the total time complexity for this solution is $O(n)$." |
618 | 618 | ] |
619 | 619 | }, |
| 620 | + { |
| 621 | + "cell_type": "markdown", |
| 622 | + "metadata": {}, |
| 623 | + "source": [ |
| 624 | + "## `defaultdict()`" |
| 625 | + ] |
| 626 | + }, |
| 627 | + { |
| 628 | + "cell_type": "code", |
| 629 | + "execution_count": 1, |
| 630 | + "metadata": { |
| 631 | + "ExecuteTime": { |
| 632 | + "end_time": "2018年06月24日T08:24:02.341531Z", |
| 633 | + "start_time": "2018年06月24日T08:24:02.335671Z" |
| 634 | + } |
| 635 | + }, |
| 636 | + "outputs": [], |
| 637 | + "source": [ |
| 638 | + "from collections import defaultdict" |
| 639 | + ] |
| 640 | + }, |
| 641 | + { |
| 642 | + "cell_type": "markdown", |
| 643 | + "metadata": {}, |
| 644 | + "source": [ |
| 645 | + "To initialize a defaultdict with an integer value (`0`):" |
| 646 | + ] |
| 647 | + }, |
| 648 | + { |
| 649 | + "cell_type": "code", |
| 650 | + "execution_count": 2, |
| 651 | + "metadata": { |
| 652 | + "ExecuteTime": { |
| 653 | + "end_time": "2018年06月24日T08:25:02.712379Z", |
| 654 | + "start_time": "2018年06月24日T08:25:02.682608Z" |
| 655 | + } |
| 656 | + }, |
| 657 | + "outputs": [ |
| 658 | + { |
| 659 | + "data": { |
| 660 | + "text/plain": [ |
| 661 | + "0" |
| 662 | + ] |
| 663 | + }, |
| 664 | + "execution_count": 2, |
| 665 | + "metadata": {}, |
| 666 | + "output_type": "execute_result" |
| 667 | + } |
| 668 | + ], |
| 669 | + "source": [ |
| 670 | + "d = defaultdict(int)\n", |
| 671 | + "d['test']" |
| 672 | + ] |
| 673 | + }, |
| 674 | + { |
| 675 | + "cell_type": "markdown", |
| 676 | + "metadata": {}, |
| 677 | + "source": [ |
| 678 | + "To initialize a defaultdict with a custom value, other than `0`:" |
| 679 | + ] |
| 680 | + }, |
| 681 | + { |
| 682 | + "cell_type": "code", |
| 683 | + "execution_count": 3, |
| 684 | + "metadata": { |
| 685 | + "ExecuteTime": { |
| 686 | + "end_time": "2018年06月24日T08:25:36.973182Z", |
| 687 | + "start_time": "2018年06月24日T08:25:36.962071Z" |
| 688 | + } |
| 689 | + }, |
| 690 | + "outputs": [ |
| 691 | + { |
| 692 | + "data": { |
| 693 | + "text/plain": [ |
| 694 | + "17" |
| 695 | + ] |
| 696 | + }, |
| 697 | + "execution_count": 3, |
| 698 | + "metadata": {}, |
| 699 | + "output_type": "execute_result" |
| 700 | + } |
| 701 | + ], |
| 702 | + "source": [ |
| 703 | + "d = defaultdict(lambda : 17)\n", |
| 704 | + "d['test']" |
| 705 | + ] |
| 706 | + }, |
| 707 | + { |
| 708 | + "cell_type": "markdown", |
| 709 | + "metadata": {}, |
| 710 | + "source": [ |
| 711 | + "The idea here is that you need to pass a callable function to `defaultdict()` that outputs the default value when the key is not present in the dict." |
| 712 | + ] |
| 713 | + }, |
| 714 | + { |
| 715 | + "cell_type": "code", |
| 716 | + "execution_count": 4, |
| 717 | + "metadata": { |
| 718 | + "ExecuteTime": { |
| 719 | + "end_time": "2018年06月24日T08:26:42.616985Z", |
| 720 | + "start_time": "2018年06月24日T08:26:42.606931Z" |
| 721 | + } |
| 722 | + }, |
| 723 | + "outputs": [ |
| 724 | + { |
| 725 | + "data": { |
| 726 | + "text/plain": [ |
| 727 | + "0" |
| 728 | + ] |
| 729 | + }, |
| 730 | + "execution_count": 4, |
| 731 | + "metadata": {}, |
| 732 | + "output_type": "execute_result" |
| 733 | + } |
| 734 | + ], |
| 735 | + "source": [ |
| 736 | + "int() # note that calling int() returns 0" |
| 737 | + ] |
| 738 | + }, |
| 739 | + { |
| 740 | + "cell_type": "code", |
| 741 | + "execution_count": 6, |
| 742 | + "metadata": { |
| 743 | + "ExecuteTime": { |
| 744 | + "end_time": "2018年06月24日T08:27:30.372964Z", |
| 745 | + "start_time": "2018年06月24日T08:27:30.362136Z" |
| 746 | + } |
| 747 | + }, |
| 748 | + "outputs": [ |
| 749 | + { |
| 750 | + "data": { |
| 751 | + "text/plain": [ |
| 752 | + "[1, 10, 100]" |
| 753 | + ] |
| 754 | + }, |
| 755 | + "execution_count": 6, |
| 756 | + "metadata": {}, |
| 757 | + "output_type": "execute_result" |
| 758 | + } |
| 759 | + ], |
| 760 | + "source": [ |
| 761 | + "# one more example\n", |
| 762 | + "d = defaultdict(lambda : [1, 10, 100])\n", |
| 763 | + "d['test']" |
| 764 | + ] |
| 765 | + }, |
620 | 766 | { |
621 | 767 | "cell_type": "markdown", |
622 | 768 | "metadata": {}, |
|
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