javascript LinkedList js 双向循环链表 Circular Linked List

javascript LinkedList:

function Node(elem, prev, next) {
    this.elem = elem;
    this.prev = prev ? prev : null;
    this.next = next ? prev : null;
}

function LinkedList() {
    this.length = 0;
    this.head = null;

    var that = this;
    if (arguments.length > 0) {
        var a = arguments[0];
        if (a instanceof Array) {
            a.forEach(function(elem) {
                that.push(elem);
            });
        }
    }
}

LinkedList.prototype.push = function(elem) {
    var newNode = new Node(elem);

    if (this.length === 0) {
        this.head = newNode;
        this.head.prev = newNode;
        this.head.next = newNode;
    } else {
        newNode.next = this.head;
        newNode.prev = this.head.prev;
        this.head.prev.next = newNode; // !!! CAUTION !!!
        this.head.prev = newNode;
    }
    ++this.length;
    return this.length;
};

// alias for push
LinkedList.prototype.append = function(elem) {
    return this.push(elem);
};

LinkedList.prototype.unshift = function(elem) {
    var newNode = new Node(elem);

    if (this.length === 0) {
        this.head = newNode;
        this.head.prev = newNode;
        this.head.next = newNode;
    } else {
        newNode.next = this.head;
        newNode.prev = this.head.prev;
        this.head.prev.next = newNode; // !!! CAUTION !!!
        this.head.prev = newNode;
    }
    this.head = newNode;
    ++this.length;
    return this.length;
};

LinkedList.prototype.shift = function() {
    if (this.length === 0) {
        return null;
    }
    var head = this.head,
        node = new Node(head.elem);

    head.next.prev = head.prev;
    head.prev.next = head.next;
    delete(head);

    this.head = head.next;
    --this.length;

    return node.elem;
};

LinkedList.prototype.pop = function() {
    if (this.length === 0) {
        return null;
    }
    var tail = this.head.prev,
        node = new Node(tail.elem);

    tail.prev.next = tail.next;
    tail.next.prev = tail.prev;

    delete(tail);
    --this.length;

    return node.elem;
};

LinkedList.prototype._get = function(index) {
    if (index < 0 || index >= this.length) {
        throw new DOMException("LinkedList index out of bounds!");
    }
    if (index===0) {
        return this.head;
    }
    var pivot = Math.round(this.length / 2);
    var p = null, i;
    if (index <= pivot) {
        p = this.head; // head => tail
        for (i = 0; i < index; i++) {
            p = p.next;
        }
    } else {
        p = this.head.prev; // tail => head
        for (i = this.length - 1; i > index; i--) {
            p = p.prev;
        }
    }
    return p;
};

LinkedList.prototype._delete = function(node) {
    var retNode = new Node(node.elem);

    node.prev.next = node.next;
    node.next.prev = node.prev;

    var p = node.next;
    if (node===this.head) {
        this.head = p;
    }
    node = null;

    this.length--;
    return {
        p: 0 <this.length ? p : null,
        v: retNode.elem
    }
};

LinkedList.prototype._insertBefore = function(node, elem) {
    var newNode = new Node(elem);
    newNode.next = node;
    newNode.prev = node.prev;
    node.prev.next = newNode;
    node.prev = newNode;
    ++this.length;
    return newNode;
};

LinkedList.prototype.get = function(index) {
    var p = this._get(index);
    return p.elem;
};

LinkedList.prototype.splice = function(start,deleteCount,items) {
    var p = this._get(start), o, list = new LinkedList();
    while (deleteCount--) {
        o = this._delete(p);
        p = o.p;
        list.push(o.v);
        if (null===p) {break;}
    }
    var that = this;
    if (typeof items !== "undefined") {
        var i = 0;
        if (items instanceof Array) {
            for (i = 0; i < items.length; i++) {
                p = that._insertBefore(p, items[i]);
            }
        } else if (items instanceof LinkedList) {
            for (i = 0; i < items.length; i++) {
                p = that._insertBefore(p, items.get(i));
            }
        } else {
            that._insertBefore(p, items);
        }
    }
    return list;
};

LinkedList.prototype.forEach = function(callback) {
    var p = this.head,
        index = 0;
    do {
        callback(p.elem, index);
        p = p.next;
        index++;
    } while (p != this.head);
    return this;
};

LinkedList.prototype.map = function(callback) {
    var newList = new this.__proto__.constructor();
    this.forEach(function(elem) {
        newList.push(callback(elem));
    });
    return newList;
};

LinkedList.prototype.reduce = function(callback, initValue) {
    if (this === null) {
        throw new TypeError('LinkedList.prototype.reduce ' +
            'called on null or undefined');
    }
    if (typeof callback !== 'function') {
        throw new TypeError(callback + ' is not a function');
    }
    var acc = initValue,
        p = this.head;
    do {
        acc = callback(acc, p.elem);
        p = p.next;
    } while (p != this.head);

    return acc;
};

LinkedList.prototype.join = function(sep) {
    var s = "";
    if (this.length === 0) {
        return s;
    }
    if (this.length === 1) {
        return this.head.elem;
    }
    var p = this.head;
    do {
        s += p.elem.toString() + sep;
        p = p.next;
    } while (p != this.head.prev);
    s += p.elem.toString();
    return s;
};

LinkedList.prototype.toString = function() {
    return '[' + this.join(',') + ']';
};

LinkedList.prototype.insertBeforeIndex = function(index, elem) {
    if (index === 0) {
        this.unshift(elem);
        return this.length;
    }
    if (index >this.length) {
        throw new DOMException('index out of bounds');
    }
    if (index === this.length) {
        this.append(elem);
        return this.length;
    }
    var node = new Node(elem);
    if (index === this.length-1) {
        var tail = this.head.prev;
        node.next = tail;
        node.prev = tail.prev;
        tail.prev.next = node;
        tail.prev = node;
    } else {
        var p = this._get(index);

        node.next = p;
        node.prev = p.prev;
        p.prev.next = node;
        p.next.prev = node;
    }
    ++this.length;

    return this.length;
};

　　

　　

// Array like 

// test
var list = new LinkedList();
 
for (var i = 1; i < 10; i++) {
    list.push(i);
}
for (i = 0; i < list.length; i++) {
    console.log(list.get(i));    // 1,2,3,4,5,6,7,8,9
}
 
// list.forEach(function(elem) {console.log(elem);});
var newList = list.map(function(elem) {
    return elem - 1;
});
console.log(newList.toString()); //  0,1,2,3,4,5,6,7,8
newList.shift();
console.log(newList.toString()); // 1,2,3,4,5,6,7,8
 
var oList = new LinkedList();
oList.push({ x: 2 });
oList.push({ x: 2 });
oList.push({ x: 3 });
 
var mul = oList.reduce(function(a, c) {
    return a * c.x;
}, 1);
console.log(mul); // 12

 // test 2

var a = [3, 12, 17, 16, 73, 32, 61, 46, 52, 49, 6, 5];
var list = new LinkedList(a);
console.log(list.toString());
console.log('array: ' + a.length + ' list: ' + list.length);

list.insertBeforeIndex(0, 99);
console.log(list.toString());

list.insertBeforeIndex(3, 99);
console.log(list.toString());

list.insertBeforeIndex(list.length, 100);
console.log(list.toString());

list.insertBeforeIndex(list.length-1, 98);
console.log(list.toString());

console.log(list.length);

 // test splice

function getTopN(a, n) {

    function _getMaxElem(a) {
        if (a.length === 0)
            throw "empty array";

        if (a.length === 1)
            return { index: 0, value: a[0] };

        var max = a.get(0), index = 0, c;
        for (var i = 0; i < a.length; i++) {
            c = a.get(i);
            if (c > max) {
                max = c;
                index = i;
            }
        }
        return {
            index: index,
            value: max
        }
    }

    var o = {}, b = [];
    while (n--) {
        o = _getMaxElem(a);
        b.push(o.value);
        a.splice(o.index, 1);
    }

    return b;
}

/**
 * 5 largest elements: [73,61,52,49,46]
 * -------------sorted------------------
 * [ 73, 61, 52, 49, 46, 32, 17, 16, 12, 6, 5, 3 ]
 */
var a = [3, 12, 17, 16, 73, 32, 61, 46, 52, 49, 6, 5];
var list = new LinkedList(a);
var top5 = getTopN(list, 5);
console.log('5 largest elements: [' + top5.toString() + ']');
console.log('-------------sorted------------------');
console.log(a.sort(function(a, b) { return b - a; }));