Leetcode #1820: Maximum Number of Accepted Invitations
In this guide, we solve Leetcode #1820 Maximum Number of Accepted Invitations in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
There are m boys and n girls in a class attending an upcoming party. You are given an m x n integer matrix grid, where grid[i][j] equals 0 or 1.
Quick Facts
- Difficulty: Medium
- Premium: Yes
- Tags: Depth-First Search, Graph, Array, Matrix
Intuition
The data forms a graph, so we should explore nodes and edges systematically.
A traversal ensures we visit each node once while maintaining the needed state.
Approach
Build an adjacency list and traverse with BFS or DFS.
Aggregate results as you visit nodes.
Steps:
- Build the graph.
- Traverse with BFS/DFS.
- Accumulate the required output.
Example
Input: grid = [[1,1,1],
[1,0,1],
[0,0,1]]
Output: 3
Explanation: The invitations are sent as follows:
- The 1st boy invites the 2nd girl.
- The 2nd boy invites the 1st girl.
- The 3rd boy invites the 3rd girl.
Python Solution
class Solution:
def maximumInvitations(self, grid: List[List[int]]) -> int:
def find(i):
for j, v in enumerate(grid[i]):
if v and j not in vis:
vis.add(j)
if match[j] == -1 or find(match[j]):
match[j] = i
return True
return False
m, n = len(grid), len(grid[0])
match = [-1] * n
ans = 0
for i in range(m):
vis = set()
ans += find(i)
return ans
Complexity
The time complexity is . The space complexity is O(V).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.