JavaScript数组系列问题:数组差集

JavaScript求出两个数组的差集,下面是我实现的方法

function arrayDiffSet(a, b) {

    if ((!a || !a.length) && (b && b.length)) {
        return b
    } else if ((!b || !b.length) && (a && a.length)) {
        return a
    }

    var aMap = {},
        _aMap = {},
        _bMap = {};

    for (var i = 0, length = a.length; i < length; i++) {
        aMap[a[i]] = _aMap[a[i]] = true;
    }

    for (var i = 0, length = b.length; i < length; i++) {
        if (aMap[b[i]]) {
            delete _aMap[b[i]];
        } else {
            _bMap[b[i]] = true;
        }
    }

    return {
        a: Object.keys(_aMap),
        b: Object.keys(_bMap)
    }

}

function generateRandomArray(length, range) {
    var result = [];
    for (var i = 0; i < length; i++) {
        result[result.length] = Math.floor(Math.random() * range);
    }
    return result
}

var a = generateRandomArray(5, 10);
var b = generateRandomArray(10, 10);

console.log('a', a);
console.log('b', b);

console.time('start');
console.log(arrayDiffSet(a, b));
console.timeEnd('start');

----------但是这个方法还有下面两点:
1、扩展性差,如果我需要返回的差集不去重,那需要再重新写一个方法;
2、没有办法对对象数组求差集;

所以在这里想问问各位大神有没有更优的解决方案

阅读 1.8k
评论 更新于 2017-03-26
    2 个回答
    小明
    • 1.3k

    我代码写的不好。

    不过求差集好像filter一下就可以了。

    var a = generateRandomArray(5, 10);
    var b = generateRandomArray(10, 10);
    
    // 不去重
    var result = {
        a: a.filter(el => !b.includes(el)),
        b: b.filter(el => !a.includes(el))
    }
    
    // 去重
    var result2 = {
        a: [...new Set(a)].filter(el => !b.includes(el)),
        b: [...new Set(b)].filter(el => !a.includes(el))
    }
    
    // 合并一下
    function diffSet(a, b, noDup) {
        if (noDup) {
            a = [...new Set(a)];
            b = [...new Set(b)];
        }
        return {
            a: a.filter(el => !b.includes(el)),
            b: b.filter(el => !a.includes(el))
        }
    }

    至于对象数组。。。太麻烦了,等你先把这个看明白了再说:lodash.isEqual


    不使用ES6:

    // 不去重
    // 使用indexOf代替includes
    
    a.filter(function(el){
        return b.indexOf(el) == -1;
    });
    
    // 去重
    // 引入index先对a自身去重
    
    a.filter(function(el, idx){
        return a.indexOf(el) == idx && b.indexOf(el) == -1;
    });
    评论 赞赏 2017-03-26

      新方法:

      /**
       * 新方法
       * @param {Object} a
       * @param {Object} b
       * @param {Object} isDup 是否不去重(默认去重)
       */
      
      
      function arrayDiffSet(a, b, isDup) {
      
          var al = a.length,
              bl = b.length;
      
          if ((!a || !al) && (b && bl)) {
              return b
          } else if ((!b || !bl) && (a && al)) {
              return a
          }
      
          var i = 0,
              aMap = {},
              _aMap = {},
              _bMap = {},
              _a = [],
              _b = [],
              temp;
      
          for (i = 0; i < al; i++) {
              temp = a[i];
              aMap[temp] = true;
              !_aMap[temp] ? _aMap[temp] = [] : '';
              _aMap[temp][_aMap[temp].length] = temp;
          }
      
          for (i = 0; i < bl; i++) {
              temp = b[i];
              if (aMap[temp]) {
                  delete _aMap[temp];
              } else {
                  _b[_b.length] = temp;
                  _bMap[temp] = true;
              }
          }
      
          if (isDup) {
              for (var item in _aMap) {
                  _a = _a.concat(_aMap[item]);
              }
      
              return {
                  a: _a,
                  b: _b
              }
          }
      
          return {
              a: Object.keys(_aMap),
              b: Object.keys(_bMap)
          }
      
      }
      
      function generateRandomArray(length, range) {
          var result = [];
          for (var i = 0; i < length; i++) {
              result[result.length] = Math.floor(Math.random() * range);
          }
          return result
      }
      
      var a = generateRandomArray(1000, 1000);
      var b = generateRandomArray(1000, 1000);
      
      console.log(a);
      console.log(b);
      
      console.time('start');
      console.log(arrayDiffSet(a, b, true));
      console.timeEnd('start');
      

      另附:jQuery也是可以去重的
      var a = [1, 2, 3, 4];
      var b = [1, 2, 4, 5];
      var c = $(a).not(b);
      c = c.toArray(); // [3]

      评论 赞赏 2017-03-26
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