Leetcode #649: Dota2 Senate
In this guide, we solve Leetcode #649 Dota2 Senate 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
In the world of Dota2, there are two parties: the Radiant and the Dire. The Dota2 senate consists of senators coming from two parties.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Greedy, Queue, String
Intuition
A locally optimal choice leads to a globally optimal result for this structure.
That means we can commit to decisions as we scan without backtracking.
Approach
Sort or preprocess if needed, then repeatedly take the best available local choice.
Maintain the minimal state necessary to validate the greedy decision.
Steps:
- Sort or preprocess as needed.
- Iterate and pick the best local option.
- Track the current solution.
Example
Input: senate = "RD"
Output: "Radiant"
Explanation:
The first senator comes from Radiant and he can just ban the next senator's right in round 1.
And the second senator can't exercise any rights anymore since his right has been banned.
And in round 2, the first senator can just announce the victory since he is the only guy in the senate who can vote.
Python Solution
class Solution:
def predictPartyVictory(self, senate: str) -> str:
qr = deque()
qd = deque()
for i, c in enumerate(senate):
if c == "R":
qr.append(i)
else:
qd.append(i)
n = len(senate)
while qr and qd:
if qr[0] < qd[0]:
qr.append(qr[0] + n)
else:
qd.append(qd[0] + n)
qr.popleft()
qd.popleft()
return "Radiant" if qr else "Dire"
Complexity
The time complexity is , and the space complexity is . The space complexity is .
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.