Digit Count in Range — LeetCode 1067 Python Solution
HardLeetCode PremiumMathDynamic Programming
- Problem
- #1067
- Pattern
- Dynamic Programming
- Reading time
- 4 min
- Source
- leetcode.com
The problem
Given a single-digit integer d and two integers low and high, return the number of times that d occurs as a digit in all integers in the inclusive range [low, high].
Example
- Input
- d = 1, low = 1, high = 13
- Output
- 6
- Explanation
- The digit d = 1 occurs 6 times in 1, 10, 11, 12, 13.
Python solution
Python
class Solution:
def digitsCount(self, d: int, low: int, high: int) -> int:
return self.f(high, d) - self.f(low - 1, d)
def f(self, n, d):
@cache
def dfs(pos, cnt, lead, limit):
if pos <= 0:
return cnt
up = a[pos] if limit else 9
ans = 0
for i in range(up + 1):
if i == 0 and lead:
ans += dfs(pos - 1, cnt, lead, limit and i == up)
else:
ans += dfs(pos - 1, cnt + (i == d), False, limit and i == up)
return ans
a = [0] * 11
l = 0
while n:
l += 1
a[l] = n % 10
n //= 10
return dfs(l, 0, True, True)Complexity
| Measure | Complexity |
|---|---|
| Time | O(n·m) (typical) |
| Space | O(n·m) or optimized auxiliary |
Pattern: Dynamic Programming
Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 1067. Digit Count in Range is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Dynamic Programming.
The dynamic programming guide has the Python template for the pattern and the 481 LeetCode problems that use it.
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Frequently asked questions
- How hard is LeetCode 1067. Digit Count in Range?
- LeetCode 1067. Digit Count in Range is rated Hard on LeetCode.
- What topics does LeetCode 1067. Digit Count in Range cover?
- LeetCode 1067. Digit Count in Range is tagged Math and Dynamic Programming on LeetCode.
- Is LeetCode 1067. Digit Count in Range a premium problem?
- Yes. LeetCode 1067. Digit Count in Range is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.