深入解析桶排序算法及Node.js上JavaScript的代码实现

'use strict';

/////////////////////////////////////////////////
// 桶排序
/////////////////////////////////////////////////
var _this = this
  , L = require('linklist');//链表

/**
 * 普通数组桶排序,同步
 *
 * @param arr Array 整数数组
 * @param num 桶的个数
 *
 * @example:
 * sort([1,4,1,5,3,2,3,3,2,5,2,8,9,2,1],5)
 * sort([1,4,1,5,3,2,3,3,2,5,2,8,9,2,1],5,0,5)
 */
exports.sort = function (arr, count) {
  if (arr.length == 0) return [];
  count = count || (count > 1 ? count : 10);

  // 判断最大值、最小值
  var min = arr[0], max = arr[0];
  for (var i = 1; i < arr.length; i++) {
    min = min < arr[i] ? min : arr[i];
    max = max > arr[i] ? max : arr[i];
  }
  var delta = (max - min + 1) / count;
  // console.log(min+","+max+","+delta);

  //初始化桶
  var buckets = [];

  //存储数据到桶
  for (var i = 0; i < arr.length; i++) {
    var idx = Math.floor((arr[i] - min) / delta); // 桶索引

    if (buckets[idx]) {//非空桶
      var bucket = buckets[idx];
      var insert = false;//插入标石
      L.reTraversal(bucket, function (item, done) {
        if (arr[i] <= item.v) {//小于，左边插入
          L.append(item, _val(arr[i]));
          insert = true;
          done();//退出遍历
        }
      });
      if (!insert) { //大于，右边插入
        L.append(bucket, _val(arr[i]));
      }
    } else {//空桶
      var bucket = L.init();
      L.append(bucket, _val(arr[i]));
      buckets[idx] = bucket; //链表实现
    }
  }

  var result = [];
  for (var i = 0, j = 0; i < count; i++) {
    L.reTraversal(buckets[i], function (item) {
      // console.log(i+":"+item.v);
      result[j++] = item.v;
    });
  }
  return result;
}

//链表存储对象
function _val(v) {
  return {v: v}
}

var algo = require('./index.js');
var data = [ 7, 36, 65, 56, 33, 60, 110, 42, 42, 94, 59, 22, 83, 84, 63, 77, 67,101 ];
console.log(data);
console.log(algo.bucketsort.sort(data,5));//5个桶
console.log(algo.bucketsort.sort(data,10));//10个桶

[ 7, 36, 65, 56, 33, 60, 110, 42, 42, 94, 59, 22, 83, 84, 63, 77, 67, 101 ]
[ 7, 22, 33, 36, 42, 42, 56, 59, 60, 63, 65, 67, 77, 83, 84, 94, 101, 110 ]
[ 7, 22, 33, 36, 42, 42, 56, 59, 60, 63, 65, 67, 77, 83, 84, 94, 101, 110 ]

//产生100W条，[200,900]闭区间的数据
var data = algo.data.randomData(1000*1000,200,900);
var s1 = new Date().getTime();
algo.quicksort.sort(data);//快速排序
var s2 = new Date().getTime();
algo.bucketsort.sort(data,700);//装到700个桶
var s3 = new Date().getTime();

console.log("quicksort time: %sms",s2-s1);
console.log("bucket time: %sms",s3-s2);

quicksort time: 14768ms
bucket time: 1089ms

O(N)+O(M*(N/M)*log(N/M))=O(N+N*(logN-logM))=O(N+N*logN-N*logM)