Sam and Substrings - Hackerrank Problem Solution

Sam and Substrings

Hackerrank Problem Solution

Sam and Substrings

PROBLEM STATEMENT

Samantha and Sam are playing a numbers game. Given a number as a string, no leading zeros, determine the sum of all integer values of substrings of the string. For example, if the string is , the substrings are  and . Their sum is .

Given an integer as a string, sum all of its substrings cast as integers. As the number may become large, return the value modulo .

Function Description

Complete the substrings function in the editor below. It should return the sum of the integer values of all substrings in a string representation of a number, modulo .

substrings has the following parameter(s):

• n: the string representation of an integer

Input Format

A single line containing an integer as a string without leading zeros.

Constraints

Output Format

A single line which is sum of the substrings, 

Sample Input 0

16

Sample Output 0

23

Explanation 0

The substring of number 16 are 16, 1 and 6 which sums to 23.

Sample Input 1

123

Sample Output 1

164

Explanation 1

The sub-strings of 123 are 1, 2, 3, 12, 23, 123 which sums to 164.

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SOLUTION

import sys MOD = 1000000007 if __name__ == '__main__': N = list(map(int, list(sys.stdin.readline().strip()))) total = 0 k = 1 for i, digit in enumerate(reversed(N)): total += k * digit * (len(N) - i) % MOD k = ((10 * k) + 1) % MOD print(total % MOD)

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