Tasks Details
easy
1.
Nesting
Determine whether a given string of parentheses (single type) is properly nested.
Task Score
62%
Correctness
50%
Performance
75%
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:
class Solution { public int solution(String S); }
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 ')'.
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Java 8
Time spent on task 18 minutes
Notes
not defined yet
Code: 12:40:56 UTC,
java,
autosave
Code: 12:57:56 UTC,
java,
autosave
// you can also use imports, for example:
// import java.util.*;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> stack = new Stack<>();
if (S.length() <= 1) {
return 0;
}
for (int i=0; i<S.length(); i++) {
char chr = S.charAt(i);
if (chr == '(') {
stack.push(chr);
} else {
if (chr == ')' && stack.isEmpty()) {
return 0;
}
if (stack.pop() == '(' && chr != ')') {
return 0;
}
}
}
return 1;
}
}
Code: 12:58:01 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
// import java.util.*;
import java.util.Stack;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> stack = new Stack<>();
if (S.length() <= 1) {
return 0;
}
for (int i=0; i<S.length(); i++) {
char chr = S.charAt(i);
if (chr == '(') {
stack.push(chr);
} else {
if (chr == ')' && stack.isEmpty()) {
return 0;
}
if (stack.pop() == '(' && chr != ')') {
return 0;
}
}
}
return 1;
}
}
Analysis
Code: 12:58:04 UTC,
java,
final,
score:
62
// you can also use imports, for example:
// import java.util.*;
import java.util.Stack;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> stack = new Stack<>();
if (S.length() <= 1) {
return 0;
}
for (int i=0; i<S.length(); i++) {
char chr = S.charAt(i);
if (chr == '(') {
stack.push(chr);
} else {
if (chr == ')' && stack.isEmpty()) {
return 0;
}
if (stack.pop() == '(' && chr != ')') {
return 0;
}
}
}
return 1;
}
}
Analysis summary
The following issues have been detected: wrong answers.
For example, for the input '' the solution returned a wrong answer (got 0 expected 1).
Analysis
expand all
Correctness tests
1.
0.008 s
OK
2.
0.008 s
OK
1.
0.008 s
WRONG ANSWER,
got 0 expected 1
simple_grouped
simple grouped positive and negative test, length=22
simple grouped positive and negative test, length=22
✘
WRONG ANSWER
got 1 expected 0
got 1 expected 0
1.
0.008 s
OK
2.
0.008 s
WRONG ANSWER,
got 1 expected 0
3.
0.008 s
OK
1.
0.008 s
OK
2.
0.004 s
OK
3.
0.004 s
OK
expand all
Performance tests
large1
simple large positive and negative test, 10K or 10K+1 ('s followed by 10K )'s
simple large positive and negative test, 10K or 10K+1 ('s followed by 10K )'s
✘
WRONG ANSWER
got 1 expected 0
got 1 expected 0
1.
0.032 s
OK
2.
0.032 s
WRONG ANSWER,
got 1 expected 0
3.
0.004 s
OK
1.
0.224 s
OK
2.
0.008 s
OK
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+
sequence of full trees of the form T=(TT), depths [1..10..1], with/without unmatched ')' at the end, length=49K+
✔
OK
1.
0.064 s
OK
2.
0.068 s
OK
3.
0.004 s
OK
broad_tree_with_deep_paths
string of the form (TTT...T) of 300 T's, each T being '(((...)))' nested 200-fold, length=1 million
string of the form (TTT...T) of 300 T's, each T being '(((...)))' nested 200-fold, length=1 million
✔
OK
1.
1.216 s
OK
2.
0.004 s
OK