In most of the modern programming language I have learnt, such as C++ and Python, as well as Javascript, the memory allocation for array data structure is like this:
/* (e.g.) */ var a = [["a", "b", 'c"], [1, 2, 3], ["甲", "乙", "丙"]] //Java-script
// /* Memory allocation in order */ "a" --> 'b" --> "c" --> 1 --> 2 --> 3 --> "甲" --> "乙" --> "丙"
Little thought
Suppose I am gonna store the following sets of data into an array, what’s the most best way to make it accessible most efficiently?
| Name | No | Index |
| Peter |
1 |
0 |
| Mary |
5 |
1 |
| Lily |
30 |
2 |
| Jonathan |
25 |
3 |
Given that the items can be accessed by knowing the index, I have thought of 2 ways of storage
Method 1: The traditional way
var data = [["Peter", 1], ["Mary", 5], ["Lily", 30], ["Jonathan", 25]]; // /* Memory storage: */ "Peter" --> 1 --> "Mary" --> 5 --> "Lily" --> 30 --> "Jonathan" --> 25
This way is very clear and easy to understand, but may not be quite efficient to access the {No} of each element. For instance, the computer has to read pass all {Name}s of each item, and the memory access footprint is long.
Method 2: The “Split" way
var data = [["Peter", "Mary", "Lily", "Jonathan"], [1, 5, 30, 25]]; // /* Memory storage: */ "Peter" --> "Mary" --> "Lily" --> "Jonathan" --> 1 --> 5 --> 30 --> 25
To loop through all {No}s of all data items, just loop within data[1], and the memory access footprint is limited to number of data items.
To access {Name}s and {No}s, just need data[0][x] and data[1][x], where “x" is the index of the item.
There may be a problem associated with this kind of array structure, such as deleting a datum element, it has to loop through different parts of the data (can be understood as “columns" of data in a table). Nonetheless, for storing rare-updated data, I prefer the “split" way.
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