JAVA-sparse array introduction

JAVA-sparse array introduction

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1. When most of the elements in an array are 0 or an array of the same value, a sparse array can be used to save the array.
2. The sparse array is handled as follows:
   1. Record the total number of rows and columns in the array, and how many different values ​​are there.
   2. Record the elements with different values, rows, columns and values ​​in a small array, thereby reducing the size of the program
3. As shown below: the left is the original array, the right is the sparse array
4.