07/29/16

HackerRank ‘Circular Array Rotation’ Solution

Short Problem Definition:

John Watson performs an operation called a right circular rotation on an array of integers.

Link

Circular Array Rotation

Complexity:

time complexity is O(Q)

space complexity is O(1)

Execution:

Calculate the offset for every query. Watch out for index overflows and negative modulo.

Solution:
use std::io;
 
fn get_number() -> u32 {
    let mut line = String::new();
    io::stdin().read_line(&mut line).ok().expect("Failed to read line");
    line.trim().parse::<u32>().unwrap()
}
 
fn get_numbers() -> Vec<u32> {
    let mut line = String::new();
    io::stdin().read_line(&mut line).ok().expect("Failed to read line");
    line.split_whitespace().map(|s| s.parse::<u32>().unwrap()).collect()
}
 
fn main() {
    let line = get_numbers();
    let (n,k,q) = (line[0], line[1], line[2]);
    let a = get_numbers();
    for _ in 0..q {
        let m = get_number();
        let idx = ((m-(k%n)+n)%n) as usize;
        println!("{}", a[idx]);
    }
}

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07/29/16

HackerRank ‘Compare Triplets’ Solution

Short Problem Definition:

Alice and Bob each created one problem for HackerRank. A reviewer rates the two challenges, awarding points on a scale from 1 to 100  for three categories: problem clarity, originality, and difficulty.

Link

Compare Triplets

Complexity:

time complexity is O(1)

space complexity is O(1)

Execution:

This is a warmup. Follow specification.

Solution:
use std::io;
use std::cmp::Ordering;

fn get_numbers() -> Vec<u32> {
    let mut line = String::new();
    io::stdin().read_line(&mut line).ok().expect("Failed to read line");
    line.split_whitespace().map(|s| s.parse::<u32>().unwrap()).collect()
}

fn main() {
    let a = get_numbers();
    let b = get_numbers();
    
    let mut alice = 0;
    let mut bob = 0;
    
    for idx in 0..3 {
        match a[idx].cmp(&b[idx]) {
            Ordering::Less      => bob += 1,
            Ordering::Greater   => alice += 1,
            Ordering::Equal     => {},
        }
    }
 
    println!("{} {}", alice, bob);
}

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07/3/16

HackerRank ‘Divisible Sum Pairs’ Solution

Short Problem Definition:

You are given an array of n integers and a positive integer, k. Find and print the number of (i,j) pairs where i < j and ai + aj is evenly divisible by k.

Link

Divisible Sum Pairs

Complexity:

time complexity is O(N^2)

space complexity is O(1)

Execution:

Brute force search.

Solution:
n,k = raw_input().strip().split(' ')
n,k = [int(n),int(k)]
a = map(int,raw_input().strip().split(' '))
count=0
for i in xrange(len(a)):
    for j in xrange(i+1,len(a)):
        if (a[i]+a[j]) % k == 0:
            count+=1
        
print count

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