javascript 求最大前5个数; 对象深拷贝 deep copy

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* 用数组

function getTopN(a, n) {

	function _cloneArray(aa) {

    	var n = aa.length, a = new Array(n);

    	for (var i = 0; i < n; i++) {

    		a[i] = aa[i];

    	}

    	return a;

    }

    function _getMaxElem(a) {

        if (a.length === 0)

        	throw "empty array"; 

        if (a.length === 1)

            return { index: 0, value: a[0] };        

        var max = a[0],

            index = 0;

        for (var i = 0; i < a.length; i++) {

            if (a[i] > max) {

                max = a[i];

                index = i;

            }

        }

        return {

            index: index,

            value: max

        }

    }

    var o = {}, b = [], c = _cloneArray(a);;

    while (n--) {

        o = _getMaxElem(c);

        b.push(o.value);

        c.splice(o.index, 1);

    }

    return b;

}

// test

/*

var a= [];

for (var i = 0; i < 12; i++) {

    a.push(Math.round(Math.random()*100));

}

console.log(a);

*/

var a = [3, 12, 17, 16, 73, 32, 61, 46, 52, 49, 6, 5];

var b = getTopN(a, 5);

console.log('max elements: [' + b.toString() + ']');  // [73,61,52,49,46]

console.log('-------------sorted------------------');

console.log(a.sort(function(a, b) { return b - a; }));

test getTopN

* 用链表 []

+ splice方法点击查看我自己的博客 https://www.cnblogs.com/mingzhanghui/p/9317179.html

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;

}

/**

 * max 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('max elements: [' + top5.toString() + ']');

console.log('-------------sorted------------------');

console.log(a.sort(function(a, b) { return b - a; }));

-------------------------------------------------------------------

clone object:

function clone(obj) {

    // Handle the 3 simple types, and null or undefined

    if (null == obj || "object" != typeof obj) return obj;

    var copy;

    // Handle Date

    if (obj instanceof Date) {

        copy = new Date();

        copy.setTime(obj.getTime());

        return copy;

    }

    // Handle Array

    if (obj instanceof Array) {

    	var n = obj.length;

    	copy = new Array(n);

    	for (var i = 0; i < n; i++) {

    		copy[i] = obj[i];

    	}

    	return copy;

    }

    // Handle Object

    if (obj instanceof Object) {

        copy = {};

        for (var attr in obj) {

            if (obj.hasOwnProperty(attr)) {

            	copy[attr] = clone(obj[attr]); // 双向循环列表会无限递归 stackoverflow

            }

        }

        return copy;

    }

    throw new Error("Unsupported type for copying object...");

}

// test:

// test

var o = { name1:[1,2,3,4], name2:{ inner1:[1,2], inner2: null, inner3:{a:[1,2], b:"this is good", c:3, d:null, e:undefined}} };

var p = clone(o);

console.log(o===p);   // false

console.log(o.toString()===p.toString()); // true

console.log('----------');

var date1 = new Date();

var date2 = clone(date1);

var date3 = date1;

console.log(date2===date1);  // false;

console.log(date2.getTime()===date1.getTime());  // true

console.log(date3===date1);   // true;

test clone