| # | Title | Solutions | Video | Difficulty | Tag

|-----|----------------|---------------|--------|-------------|-------------

|2001|[Number of Pairs of Interchangeable Rectangles](https://leetcode.com/problems/number-of-pairs-of-interchangeable-rectangles/)|[Python3](../master/python3/_2001.py)||Medium||

|2000|[Reverse Prefix of Word](https://leetcode.com/problems/reverse-prefix-of-word/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_2000.java)||Easy||

|1996|[The Number of Weak Characters in the Game](https://leetcode.com/problems/the-number-of-weak-characters-in-the-game/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1996.java)||Medium||

|1995|[Count Special Quadruplets](https://leetcode.com/problems/count-special-quadruplets/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1995.java)||Easy||

classSolution:

definterchangeableRectangles(self,rectangles:List[List[int]])->int:

cnt=Counter()

forw,hinrectangles:

cnt[Fraction(w,h)]+=1

forvalueincnt.values():

ans+=value* (value-1)//2