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Program to count number of ways we can make a list of values by splitting numeric string in Python
Suppose we have a strings s. The s is containing digits from 0 - 9 and we also have another number k. We have to find the number of different ways that s can be represented as a list of numbers from [1, k]. If the answer is very large then return result mod 10^9 + 7.
So, if the input is like s = "3456" k = 500, then the output will be 7, as we can represent s like [3, 4, 5, 6], [34, 5, 6], [3, 4, 56], [3, 45, 6], [34, 56], [345, 6], [3, 456]
To solve this, we will follow these steps −
m := 10^9 + 7
N := size of s
dp := a list of size (N + 1) and fill with 0
dp[N] := 1
for i in range N − 1 to 0, decrease by 1, do
curr_val := 0
for j in range i to N, do
curr_val := curr_val * 10 + (s[j] as number)
if curr_val in range 1 through k, then
dp[i] :=(dp[i] + dp[j + 1]) mod m
otherwise,
come out from the loop
return dp[0]
Let us see the following implementation to get better understanding −
Example
class Solution: def solve(self, s, k): m = 10 ** 9 + 7 N = len(s) dp = [0] * (N + 1) dp[N] = 1 for i in range(N − 1, −1, −1): curr_val = 0 for j in range(i, N): curr_val = curr_val * 10 + int(s[j]) if 1 <= curr_val <= k: dp[i] = (dp[i] + dp[j + 1]) % m else: break return dp[0] ob = Solution() s = "3456" k = 500 print(ob.solve(s, k))
Input
"3456", 500
Output
7
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