Substring Printer c-python convertion

Convert a C program that prints the last X characters of a string to equivalent Python code

Understand the Problem

Problem Statement

Convert the provided C code to Python so that the Python program executes successfully and produces the same output as the C version.

The C program reads a string and an integer X, then prints the last X characters of the string using pointer arithmetic.

Constraints

Input string length is at most 100 characters
Integer X is positive and less than or equal to string length
String contains only printable ASCII characters

Examples

Example 1

Input

Hello World
5

Output

World

Explanation

The last 5 characters of 'Hello World' are 'World'

Example 2

Input

Programming
4

Output

ming

Explanation

The last 4 characters of 'Programming' are 'ming'

Example 3

Input

test
2

Output

st

Explanation

The last 2 characters of 'test' are 'st'

Solution

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char str[101];
    int len, X;
    scanf("%s%n%d", str, &len, &X);
    printf("%s", str + len - X);
    return 0;
}

Time:O(1)

Space:O(1)

Approach:

The C solution uses the %n format specifier in scanf to get the number of characters read into the string, which gives us the length. Then it uses pointer arithmetic (str + len - X) to point to the position X characters from the end of the string, and prints from that position to the end.

Key points:

%s reads the string
%n stores the number of characters read so far in len
%d reads the integer X
str + len - X creates a pointer to the desired starting position

Visual Explanation

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