Leetcode #2232: Minimize Result by Adding Parentheses to Expression
In this guide, we solve Leetcode #2232 Minimize Result by Adding Parentheses to Expression 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
You are given a 0-indexed string expression of the form "
+ " where and represent positive integers. Add a pair of parentheses to expression such that after the addition of parentheses, expression is a valid mathematical expression and evaluates to the smallest possible value.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: String, Enumeration
Intuition
We need to scan characters while tracking positions or counts.
A simple state machine keeps the logic precise.
Approach
Iterate through the string once and update the state for each character.
Use a map or array if you need fast lookups.
Steps:
- Iterate through characters.
- Maintain necessary state.
- Build or validate the output.
Example
Input: expression = "247+38"
Output: "2(47+38)"
Explanation: The expression evaluates to 2 * (47 + 38) = 2 * 85 = 170.
Note that "2(4)7+38" is invalid because the right parenthesis must be to the right of the '+'.
It can be shown that 170 is the smallest possible value.
Python Solution
class Solution:
def minimizeResult(self, expression: str) -> str:
l, r = expression.split("+")
m, n = len(l), len(r)
mi = inf
ans = None
for i in range(m):
for j in range(n):
c = int(l[i:]) + int(r[: j + 1])
a = 1 if i == 0 else int(l[:i])
b = 1 if j == n - 1 else int(r[j + 1 :])
if (t := a * b * c) < mi:
mi = t
ans = f"{l[:i]}({l[i:]}+{r[: j + 1]}){r[j + 1:]}"
return ans
Complexity
The time complexity is O(n). The space complexity is O(1) to O(n).
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.