使用堆实现Top K 算法 JS 实现

1. 使用堆算法实现Top，时间复杂度为 O(LogN)

function top(arr,comp){if(arr.length == 0){return ;}var i = arr.length / 2 | 0 ;for(;i >= 0; i--){if(comp(arr[i], arr[i * 2])){exch(arr, i, i*2);}if(comp(arr[i], arr[i * 2 + 1])) {exch(arr, i, i*2 + 1);}}return arr[0];}function exch(arr,i,j){var t = arr[i];arr[i] = arr[j];arr[j] = t;}

2. 调用K次堆实现，时间复杂度为 O(K * LogN)

function topK(arr,n,comp){if(!arr || arr.length == 0 || n <=0 || n > arr.length){return -1;}var ret  = new Array();for(var i = 0;i < n; i++){var max = top(arr,comp);ret.push(max);arr.splice(0,1);}return ret;}

3.测试

var ret = topK(new Array(16,22,91,0,51,44,23),3,function (a,b){return a < b;});console.log(ret);