The front end - data structures and algorithms (a)

1. Basic details of the data structure based on practical

Data structure (data structure [strʌktʃə (r)]) is a computer store, organize data;

(Algorithm [ælɡərɪðəm]) algorithm is a solution to the problem / steps and strategies;

Data structure Array

Js array structure is very simple (browser help us deal with a good package)

You can store different types of data values
An array of storage capacity along with automatic scaling content
Provides a method of operating the array Array.prototype

Advantage : based on the index to find and get a direct, high efficiency;

Drawbacks : The intermediate insert and delete, performance is very low ( an array of collapse and delete optimization of intermediate terms)

Stack stack structure

Last out;
Only some operations: adding comprises (push) and delete (the stack);
Recursive algorithm infinite recursion stack overflow occurs.

Stack method:

class Stack {
    container = [];
    // 进栈
    enter(element) {
        this.container.unshift(element);
    }
    // 出栈
    leave() {
        return this.container.shift();
    }
    // stack length 
    size () {
         return  the this .container.length;
    }
    // get results stack 
    value () {
         return  the this .container.slice (0 );
    }
}
let sk = new Stack;

Interview a:

There are six elements, in the order of 654 321 into the stack (center can always pop), which asked the stack is not legal :( c: After following the principles advanced out )
A: 5 4 3 6 1 2
B: 4 5 3 2 1 6 
C: 3 4 6 5 2 1 
D: 2 3 4 1 5 6

Interview II: decimal binary transfer

For example: 58 => 111010

/*
* Ideas: the decimal number is divisible by 2 and with (because the binary is full 2 into 1)
* Get the number of the remaining n% 2
* To obtain its quotient n / 2 (when the value 0 is divisible stop)
* Quotient continue to spend time divided by two until the quotient is 0 so far; all the remainder from the tail to the top of the order on the link;
*/

// Method NumberObject.toString. 1 (the radix) 
var NUM = 58 ;
num.toString(2);

//方法2
Numer.protype.decimal2binary = function decimal2binary(){
   SK the let = new new Stack, decimalNum = the this .valueOf ();
    IF (decimalNum == 0) return '0' // negative 0, since 0 is converted to a binary 0 
   the while (decimalNum> 0 ) {
      sk.enter(decimalNum%2);
      decimalNum = Math.floor(decimalNum/2);
   }  
    return sk.value().join('')
} 

console.log((10).decimal2binary() );

Queue queue structure

FIFO
Delete allows the front end, a rear end allowing the insertion;
Special: Priority Queue

class Queue {
    container = [];
    // 进入
    enter(element) {
        this.container.push(element);
    }
    // 离开
    leave() {
        return this.container.shift();
    }
    // length of the queue 
    size () {
         return  the this .container.length;
    }
    // Get result queue 
    value () {
         return  the this .container.slice (0 );
    }
}

Interview questions: flower drum transfer

N individuals play games together, form a circle, from 1 count start, count to M people automatically eliminated; the last remaining person will win, the last remaining ask which one is the original?

function game(n, m) {
    let qe = new Queue;
    for (let i = 0; i < n; i++) {
        qe.enter(i + 1);
    }

    the while (qe.size ()>. 1) { // when only one loop terminates 
        for (the let I = 0; I <m -. 1; I ++) { // not chosen one re-added to the queue 
            qe .enter (qe.leave ());
        }
        qe.leave();
    }

    return qe.value().toString();
}
console.log(game(8, 5)); //3

The front end - data structures and algorithms (a)

Guess you like