11、前端知识点--排序

var arr = [‘General‘,‘Tom‘,‘Bob‘,‘John‘,‘Army‘];
var resArr = arr.sort();
console.log(resArr);//输出   ["Army", "Bob", "General", "John", "Tom"]
var arr2 = [30,10,111,35,1899,50,45];
var resArr2 = arr2.sort();
console.log(resArr2);//输出   [10, 111, 1899, 30, 35, 45, 50]

var arr3 = [30,10,111,35,1899,50,45];
arr3.sort(function(a,b){
	return a - b;
})
console.log(arr3);//输出  [10, 30, 35, 45, 50, 111, 1899]
		
var arr4 = [30,10,111,35,1899,50,45];
arr4.sort(function(a,b){
	return b - a;
})
console.log(arr4);//输出 [1899, 111, 50, 45, 35, 30, 10]

var arr5 = [{id:10},{id:5},{id:6},{id:9},{id:2},{id:3}];
arr5.sort(function(a,b){
    return a.id - b.id
})
console.log(arr5);
//输出新的排序
//		{id: 2}
//		{id: 3}
//		{id: 5}
//		{id: 6}
//		{id: 9}
//		{id: 10}

var arr6 = [{id:10,age:2},{id:5,age:4},{id:6,age:10},{id:9,age:6},{id:2,age:8},{id:10,age:9}];
arr6.sort(function(a,b){
    if(a.id === b.id){//如果id相同，按照age的降序
        return b.age - a.age
    }else{
        return a.id - b.id
    }
})
console.log(arr6);
//输出新的排序
//		{id: 2, age: 8}
//		{id: 5, age: 4}
//		{id: 6, age: 10}
//		{id: 9, age: 6}
//		{id: 10, age: 9}
//		{id: 10, age: 2}

//冒泡排序
function bubbleSort(arr){
    var i = j = 0;
    for(i=1;i<arr.length;i++){
        for(j=0;j<=arr.length-i;j++){
            var temp = 0;
            if(arr[j]>arr[j+1]){
                    temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
            }
        }
    }
}

//快速排序
function quickSort(arr,l,r){
    if(l < r){
        var i = l, j = r, x = arr[i];
        while(i<j){
            while(i<j && arr[j]>x){
                j--;
                if(i<j) 
                //这里用i++，被换过来的必然比x小，赋值后直接让i自加，不用再比较，可以提高效率
                arr[i++] = arr[j];
                while(i<j && arr[i]<x){
                i++;            
                if(i<j){
                    //这里用j--，被换过来的必然比x大，赋值后直接让j自减，不用再比较，可以提高效率
                    arr[j--] = arr[i];
                }
                }
            }
            arr[i] = x;
            quickSort(arr, l, i-1);
            quickSort(arr, i+1, r);
    }
}

//将两个按值有序序列合并成一个按值有序序列，则称之为二路归并排序
function merge(left, right) {
    var result = [],
    il = 0,
    ir = 0;    
    while (il < left.length && ir < right.length) {
        if (left[il] < right[ir]) {
            result.push(left[il++]);
        } else {
            result.push(right[ir++]);
        }
    }    
    while(left[il]){
        result.push(left[il++]);
    }   
    while(right[ir]){
        result.push(right[ir++]);
    }    
    return result;
}