Sparse array)

The so-calledSparse arrayThat is, most of the content values in the array are not used (or both are zero), and only a few spaces in the array are used. This results in a waste of memory space. To save memory space and do not affect the original content values in the array, we can use a compression method to represent the content of a sparse array.

Suppose there is a 9*7 array with the following content:

In this array, There are 63 spaces, but only five elements are used, resulting in a waste of 58 Element Spaces. We will use a sparse array to redefine this array as follows:

In the sparse array, the first part records the number of columns and rows of the original array, the number of elements used, and the second part records the position and content of elements in the original array. After compression, We need to declare an array with a size of 63. After compression, we only need to declare an array with a size of 6*3 and only need 18 buckets.