学习中的算法

洗牌算法

interface Card {
	id: number,
	name: string
}
type Cards<Card> = Card[];

type Pos = number;

function shuffle<Card>(cards: Cards<Card>):void {
	const len = cards.length;
	for (let cur = 0; cur < len ;cur++ ) {
		const pos:Pos = ~~(Math.random()*len);
		[cards[pos],cards[cur]] = [cards[cur],cards[pos]];
	}
}

import random
def shuffle(cards: int[]):
	i:int = len(cards) - 1
	while i:
		i -= 1
		pos = random.randint(0,len(cards))
		cards[i],cards[pos] = cards[pos],cards[i]
shuffle([1,2,3])

循环打印数组

import "dart:math" as math;

enum Direction {
     top,
    left,
  right,
  bottom
}

void main() {
  Direction cur_direction = Direction.top;
  int circle = 1;
  int curX = 0;
  int curY = 0;
  List<int> arr = [
    0,1,2,
    3,4,5,
    6,7,8,
  ];
  List<int> res = [];
  int width = math.sqrt(arr.length).toInt();

  while (circle < width - 1) {
      // 当前环   \\
      // 执行第一轮 \\
      if (cur_direction == Direction.top) {
        while (curX < width - circle) {
          res.add(arr[curX + curY * width]);
          curX++;
        }
        cur_direction = Direction.left;
      }
      if (cur_direction == Direction.left) {
        while (curY < width - circle) {
          res.add(arr[curX + curY * width]);
          curY++;
        }
        cur_direction = Direction.bottom;
      }
      if (cur_direction == Direction.bottom) {
        while (curX > circle - 1) {
          res.add(arr[curX + curY * width]);
          curX--;
        }
        cur_direction = Direction.right;
      }
      if (cur_direction == Direction.right) {
        while (curY > circle - 1) {
          res.add(arr[curX + curY * width]);
          curY--;
        }
        cur_direction = Direction.top;
      }
      circle++;
  }
  print(res);
}

KMP Next 数组

List<int> getNext(String text){
	List<int> next = List.generate(text.length,(_)=> -1);
	int prefix = -1;
	int suffix = 0;

	while (suffix < text.length) {
		if (suffix === -1 || )
	}
}
void main(){
	print(getNext("ababa"));
}

前缀树