前端面试算法题

数组去重

function unique(arr) {
    var result = {},newArr = [];
    for(var i=0;i<arr.length;i++){
        if(!result[arr[i]]){
            newArr.push(arr[i]);
            result[arr[i]]=1;
        }
    }
    return newArr;
}

 插入排序---直接插入排序，时间算法复杂度O  (n^2)

function insertSort(a)  
{  
    for(var i= 1; i<a.length; i++){  
        if(a[i] < a[i-1]){               
            var j= i-1;   
            var x = a[i];          
            a[i] = a[i-1];        
            while(x < a[j]){   
                a[j+1] = a[j];  
                j--;          
            }  
            a[j+1] = x;       
        }  
    }        
    console.log(a)
}  

冒泡排序---时间复杂度O(n^2)

function bubbleSort( a ,n){  
    for(var i =0 ; i< n-1; ++i) {  
        for(var j = 0; j < n-i-1; ++j) {  
            if(a[j] > a[j+1])  
            {  
                var tmp = a[j] ; a[j] = a[j+1] ;  a[j+1] = tmp;  
            }  
        }  
    }  
console.log(a)
}  

 两个有序数组合并为一个有序数组(两种方法都可以)

function mergeList(a,b) {
    var c= [],i=0,j=0,k=0;
    while(i<a.length && j< b.length){
        if(a[i]<=b[j]){
            c.push(a[i]);
            i++;
        }else{
            c.push(b[j]);
            j++;
        }
    }
    while(i<a.length){
        c.push(a[i]);
        i++;
    }
    while(j<a.length){
        c.push(b[j]);
        j++;
    }
    return c;
}

function merge(left, right) {
  var tmp = [];

  while (left.length && right.length) {
    if (left[0] < right[0])
      tmp.push(left.shift());
    else
      tmp.push(right.shift());
  }

  return tmp.concat(left, right);
}