How to read files via redirection

Abstract

In this blog post we’ll learn how to read a file as input and write the output to a file using redirection.

Maximum Flow algorithm

Below are implementations of the Ford-Fulkerson algorithm to compute the maximum flow in a graph with integer capacities. Breadth first search is used to find paths from the source to the target which makes this the Edmonds-Karp algorithm. To learn about this topic I recommend reading the references.

Read input of unknown length

Problem:
Suppose you are given the following input:

5 22 9 813 13
77 98 93 51
5 3 1 5 7 1 3
9 1

Your task is to print out the sum of the numbers in each line, e.g. the sum for the first line is

5 + 22 + 9 + 813 + 13 = 862

So the output should be:

862
319
25
10

The problem here is that you don’t know how many lines you are given and how many numbers there are in each line. How can you solve this problem in Python and C++?

How to check if a number is palindromic

Suppose you are given an integer. How can you check whether the number is palindromic, i.e. you get the same number if you read its digits backwards?

Can you spot the mistake – Part 3

Below is a Python 3.4 program that is supposed to return the number of digits of an integer. However, it does not work correctly.

Next permutation in Python 3.4

In this blog post we will examine how we can compute the next lexicographic permutation of a list. We will implement the algorithm in Python 3.4.

Fast I/O methods for competitive programming

In this blog post we will have a look at fast I/O methods for competitive programming in C++, Java and Python.

Read input without knowing the number of lines

In this blog post I will describe how to read the input without knowing how many lines the input has.

Permutations in Python 3.4

In this blog post I will describe how we can create permutations in Python 3.4.

Counting the letter frequency in a string (Python 3.4)

In this blog post I will describe how to count the letter frequency in a string. We will look at two implementations, one that uses an array and the ASCII code and another that uses a dictionary.