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1996. The Number of Weak Characters in the Game

Difficulty Topics

Description

You are playing a game that contains multiple characters, and each of the characters has two main properties: attack and defense. You are given a 2D integer array properties where properties[i] = [attacki, defensei] represents the properties of the ith character in the game.

A character is said to be weak if any other character has both attack and defense levels strictly greater than this character's attack and defense levels. More formally, a character i is said to be weak if there exists another character j where attackj > attacki and defensej > defensei.

Return the number of weak characters.

 

Example 1:

Input: properties = [[5,5],[6,3],[3,6]]
Output: 0
Explanation: No character has strictly greater attack and defense than the other.

Example 2:

Input: properties = [[2,2],[3,3]]
Output: 1
Explanation: The first character is weak because the second character has a strictly greater attack and defense.

Example 3:

Input: properties = [[1,5],[10,4],[4,3]]
Output: 1
Explanation: The third character is weak because the second character has a strictly greater attack and defense.

 

Constraints:

  • 2 <= properties.length <= 105
  • properties[i].length == 2
  • 1 <= attacki, defensei <= 105

Solution

the-number-of-weak-characters-in-the-game.py
class Solution:
    def numberOfWeakCharacters(self, A: List[List[int]]) -> int:
        A.sort(key = lambda x : (x[0], -x[1]))
        res = 0
        stack = []

        for a, b in A:
            while stack and a > stack[-1][0] and b > stack[-1][1]:
                res += 1
                stack.pop()

            stack.append((a, b))

        return res