javascript实现数据结构：串--堆分配存储表示

堆分配存储表示

这种存储表示的特点是，仍以一组地址连续的存储单元存放串值字符序列，但它们的存储空间是在程序执行过程中动态分配而得。

结构图：

实现：

function HString(){
    this.ch = {};
    this.length = 0;
  }
  exports.HString = HString;
  HString.prototype = {
    // 1 <= position <= this.length.在串的第position个字符之前插入串tHString
    strInsert: function(position, tHString){
      if(position < 1 || position > this.length + 1)
        throw new Error('unexpected position');

      if(tHString.length){
        // 为插入t而腾出位置
        for(var i = this.length - 1, len = position - 1; i >= len; --i)
          this.ch[i + tHString.length] = this.ch[i];
        // s.ch[position - 1..position + tHString.length - 2] = tHString.ch[0..tHString.length - 1];
//        for(i = 0, len = tHString.length - 1; i <= len; i++)
//          this.ch[position - 1 + i] = tHString.ch[i];
        stringCopy(this.ch, tHString.ch, position - 1, tHString.length - 1, 0);

        this.length += tHString.length;
      }
    },
    strAssign: function(chars){
//      for(var i = 0, len = chars.length; i < len; i++){
//        this.ch[i] = chars[i];
//      }
      stringCopy(this.ch, chars, 0, chars.length - 1, 0);
      this.length = chars.length;
    },
    strLength: function(){
      return this.length;
    },
    strCompare: function(tHString){
      for(var i = 0, len = this.length; i < len && i < tHString.length; i++)
        if(this.ch[i] !== tHString.ch[i]) return this.ch[i] - tHString.ch[i];

      return this.length - tHString.length;
    },
    clearString: function(){
      this.ch = {};
      this.length = 0;
    },
    concat: function(s){
      var t = new HString();

      // t.ch[0..this.length - 1] = this.ch[0..this.length - 1]
      stringCopy(t.ch, this.ch, 0, this.length - 1, 0);
      t.length = this.length + s.length;
      // t.ch[this.length..t.length - 1] = s.ch[0..s.length - 1]
      stringCopy(t.ch, s.ch, this.length, s.length - 1, 0);

      return t;
    },
    substring: function(position, len){
      position = ~~position || 0;
      len = ~~len || this.length;
      if(position < 0 || position > this.length - 1 || len < 0 || len > this.length - position)
        throw new Error('unexpected paramater');

      var sub = new HString();
      stringCopy(sub.ch, this.ch, 0, len - 1, position);
      sub.length = len;

      return sub;
    },
    toString: function(){
      var s = '';
      for(var i = 0, len = this.length; i < len; i++){
        s += this.ch[i];
      }
      return s;
    }
  };

  function stringCopy(destination, target, destStart, length, targetStart){
    destStart = destStart || 0;
    length = length || target.length;
    targetStart = targetStart || 0;

    for(var i = 0; i <= length; i++ ){
      destination[destStart + i] = target[targetStart + i];
    }
  }

单元测试：

describe('HString tests', function(){
  var s = new HString();
  var t = new HString();

  it('should assign chars', function(){
    s.strAssign('hello world!');
    expect(s + '').toBe('hello world!');

    t.strAssign('jesus ');
    expect(t + '').toBe('jesus ');
  });

  it('should insert string into s', function(){
    s.strInsert(7, t);
    expect(s + '').toBe('hello jesus world!');
  });

  it('should concat string', function(){
    var ret = s.concat(t);
    expect(ret + '').toBe('hello jesus world!jesus ');
  });

  it('should get substring', function(){
    var ret = s.substring(0);
    expect(ret + '').toBe('hello jesus world!');

    ret = s.substring(5, 13);
    expect(ret + '').toBe(' jesus world!');

    ret = s.substring(3, 8);
    expect(ret + '').toBe('lo jesus');
  });
});