Memory system performing wear leveling using average erase count value and operating method thereof

A memory system comprising:

• a memory device including 0th to N-1th memory blocks, wherein N is a positive integer;
• and
• a controller having a first list and a second list,
• wherein the first list includes 0th to N-1th erase count values respectively for the 0th to N-1th memory blocks,
• wherein the second list includes 0th to N-1th difference values respectively for the 0th to N-1th memory blocks,
• wherein the controller selects a source block and a target block among the 0th to N-1th memory blocks depending on the 0th to N-1th erase count values included in the first list and the 0th to N-1th difference values included in the second list to perform a wear leveling between the source block and the target block,
• wherein the controller updates an Lth erase count value included in the first list, when performing an erase operation on an Lth memory block,
• wherein L is an integer selected between 0 to N-1, inclusive,
• wherein the controller updates a Kth difference value included in the second list with a difference between an average value of the 0th to N-1th erase count values and the Kth erase count value, after selecting a Kth memory block as the target block,
• wherein K is an integer selected between 0 to N-1, inclusive,
• wherein the controller selects an Mth memory block as the target block when first target block condition is met,
• wherein the first target block condition is that the Mth difference value included in the second list is less than a difference between the average value of the 0th to N-1th erase count values and the Mth erase count value included in the first list, and
• wherein M is an integer selected between 0 to N-1, inclusive.