Test results - Codility

Tasks Details

easy

1. Nesting

Determine whether a given string of parentheses (single type) is properly nested.

100%

A string S consisting of N characters is called properly nested if:

S is empty;

S has the form "(U)" where U is a properly nested string;

S has the form "VW" where V and W are properly nested strings.

For example, string "(()(())())" is properly nested but string "())" isn't.

Write a function:

object Solution { def solution(s: String): Int }

that, given a string S consisting of N characters, returns 1 if string S is properly nested and 0 otherwise.

For example, given S = "(()(())())", the function should return 1 and given S = "())", the function should return 0, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..1,000,000];

string S is made only of the characters '(' and/or ')'.

Solution

Programming language used Scala

Time spent on task 5 minutes

Notes

not defined yet

Task timeline

Code: 04:47:33 UTC, scala, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(S: String): Int = {
        @scala.annotation.tailrec
        def loop(idx: Int, numOpen: Int): Boolean = {
            if (idx >= S.size) numOpen == 0
            else {
                var c = S.charAt(idx)
                if (c == '(') {
                    loop(idx + 1, numOpen + 1)
                } else if (c == ')') {
                    if (numOpen == 0) false
                    else loop(idx + 1, numOpen - 1)
                } else loop(idx + 1, numOpen)
            }
        }
        
        if (loop(0, 0)) 1 else 0
    }
}

Analysis

▶

example1
example test

✔

▶

example2
example test2

✔

Code: 04:47:53 UTC, scala, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(S: String): Int = {
        @scala.annotation.tailrec
        def loop(idx: Int, numOpen: Int): Boolean = {
            if (idx >= S.size) numOpen == 0
            else {
                var c = S.charAt(idx)
                if (c == '(') {
                    loop(idx + 1, numOpen + 1)
                } else if (c == ')') {
                    if (numOpen == 0) false
                    else loop(idx + 1, numOpen - 1)
                } else loop(idx + 1, numOpen)
            }
        }
        
        if (loop(0, 0)) 1 else 0
    }
}

Analysis

▶

example1
example test

✔

▶

example2
example test2

✔

Code: 04:48:08 UTC, scala, final, score: 100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(S: String): Int = {
        @scala.annotation.tailrec
        def loop(idx: Int, numOpen: Int): Boolean = {
            if (idx >= S.size) numOpen == 0
            else {
                var c = S.charAt(idx)
                if (c == '(') {
                    loop(idx + 1, numOpen + 1)
                } else if (c == ')') {
                    if (numOpen == 0) false
                    else loop(idx + 1, numOpen - 1)
                } else loop(idx + 1, numOpen)
            }
        }
        
        if (loop(0, 0)) 1 else 0
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

▶

example1
example test

✔

▶

example2
example test2

✔

▶

negative_match
invalid structure, but the number of parentheses matches

✔

▶

empty
empty string

✔

▶

simple_grouped
simple grouped positive and negative test, length=22

✔

▶

large1
simple large positive test, 10K ('s followed by 10K )'s + )(

✔

▶

large2
simple large negative test, 10K+1 ('s followed by 10K )'s + )( + ()

✔

▶

large_full_ternary_tree
tree of the form T=(TTT) and depth 11, length=177K+

✔

▶

multiple_full_binary_trees
sequence of full trees of the form T=(TT), depths [1..10..1], with/without unmatched ')' at the end, length=49K+

✔

▶

broad_tree_with_deep_paths
string of the form (TTT...T) of 300 T's, each T being '(((...)))' nested 200-fold, length=120K+

✔