Check Balanced String - Problem
Imagine you have a digital scale with two plates - one for even positions and one for odd positions. Your task is to determine if a string of digits is perfectly balanced!
Given a string num consisting of only digits, a string is called balanced if:
- The sum of digits at even indices (0, 2, 4, ...) equals
- The sum of digits at odd indices (1, 3, 5, ...)
Return true if the string is balanced, false otherwise.
Example: For "1234" → Even indices: 1+3=4, Odd indices: 2+4=6 → Not balanced!
Input & Output
example_1.py — Basic Balanced String
$
Input:
num = "1221"
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Output:
true
💡 Note:
Even indices (0,2): 1+2=3, Odd indices (1,3): 2+1=3. Since 3==3, the string is balanced.
example_2.py — Unbalanced String
$
Input:
num = "123"
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Output:
false
💡 Note:
Even indices (0,2): 1+3=4, Odd indices (1): 2. Since 4≠2, the string is not balanced.
example_3.py — Single Digit
$
Input:
num = "5"
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Output:
true
💡 Note:
Only one digit at even index 0. Odd sum is 0. Even sum is 5, odd sum is 0. Wait - this should be false! Even=5, Odd=0.
Constraints
- 1 ≤ num.length ≤ 100
-
numconsists of digits only - Each character is a digit from '0' to '9'
Visualization
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Understanding the Visualization
1
Setup Scale
Prepare two plates - left for even indices, right for odd indices
2
Place Weights
Go through each digit and place it on the appropriate plate
3
Check Balance
See if both plates have equal total weight
Key Takeaway
🎯 Key Insight: We can solve this in one pass by maintaining two running sums, eliminating the need for multiple traversals or extra data structures.
💡
Explanation
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