In Chinese: 离散化(ie. map larger values to smaller distinct values)

please explain cordinate compression someone i can't solve a problem relating to this please help me

Let's say that in a problem, you're required to store N (1 <= N <= 10^5) elements and perform some operations on those elements (say put them in a Segment Tree). Normally, if the elements were also in the range (1, 10^5), inserting them into a data structure would be a cinch.

Say, for example, the elements are now in the range (1, 10^12). Now simply inserting elements into a Segment Tree is not possible because you cannot allocate memory for 10^12 integers. This is where coordinate compression comes into play.

Let's read in all of the possible numbers, sort them, and assign each of them a number based off of increasing order. Because N is <= 10^5, the maximum number you assign is going to be 10^5. Thus, by compressing the "coordinates", we maintain the relative order of points in a memory-efficient manner.

I hope this helps!

Good problem http://usaco.org/index.php?cpid=207&page=viewproblem2

It's when you take some coordinates, put them all in a hydraulic press. Then they become "compressed".

Check this video out.