Tasks Details
easy
1.
Brackets
Determine whether a given string of parentheses (multiple types) is properly nested.
Task Score
100%
Correctness
100%
Performance
100%
A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:
- S is empty;
- S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string;
- S has the form "VW" where V and W are properly nested strings.
For example, the string "{[()()]}" is properly nested but "([)()]" is not.
Write a function:
class Solution { public int solution(string S); }
that, given a string S consisting of N characters, returns 1 if 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..200,000];
- string S is made only of the following characters: '(', '{', '[', ']', '}' and/or ')'.
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used C#
Time spent on task 6 minutes
Notes
not defined yet
Code: 04:40:07 UTC,
cs,
verify,
result: Passed
using System;
using System.Collections.Generic;
class Solution {
public int solution(string S) {
if(S.Length==0) return 1;
Stack<char> brackets = new Stack<char>();
foreach(char c in S){
if(c=='['||c=='{'||c=='('){
brackets.Push(c);
}
else{
// return 0 if no opening brackets found and
// first bracket is closing bracket
if(brackets.Count==0) return 0;
if(c==')'){
if(brackets.Peek()=='(') brackets.Pop();
else return 0;
}
if(c=='}'){
if(brackets.Peek()=='{') brackets.Pop();
else return 0;
}
if(c==']'){
if(brackets.Peek()=='[') brackets.Pop();
else return 0;
}
}
}
if(brackets.Count==0) return 1;
return 0;
}
}
Analysis
Code: 04:40:58 UTC,
cs,
verify,
result: Passed
using System;
using System.Collections.Generic;
class Solution {
public int solution(string S) {
if(S.Length==0) return 1;
Stack<char> brackets = new Stack<char>();
foreach(char c in S){
if(c=='['||c=='{'||c=='('){
brackets.Push(c);
}
else{
// return 0 if no opening brackets found and
// first bracket is closing bracket
if(brackets.Count==0) return 0;
if(c==')'){
if(brackets.Peek()=='(') brackets.Pop();
else return 0;
}
if(c=='}'){
if(brackets.Peek()=='{') brackets.Pop();
else return 0;
}
if(c==']'){
if(brackets.Peek()=='[') brackets.Pop();
else return 0;
}
}
}
if(brackets.Count==0) return 1;
return 0;
}
}
Analysis
Code: 04:41:02 UTC,
cs,
final,
score:
100
using System;
using System.Collections.Generic;
class Solution {
public int solution(string S) {
if(S.Length==0) return 1;
Stack<char> brackets = new Stack<char>();
foreach(char c in S){
if(c=='['||c=='{'||c=='('){
brackets.Push(c);
}
else{
// return 0 if no opening brackets found and
// first bracket is closing bracket
if(brackets.Count==0) return 0;
if(c==')'){
if(brackets.Peek()=='(') brackets.Pop();
else return 0;
}
if(c=='}'){
if(brackets.Peek()=='{') brackets.Pop();
else return 0;
}
if(c==']'){
if(brackets.Peek()=='[') brackets.Pop();
else return 0;
}
}
}
if(brackets.Count==0) return 1;
return 0;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
0.057 s
OK
2.
0.059 s
OK
3.
0.057 s
OK
4.
0.059 s
OK
5.
0.058 s
OK
1.
0.058 s
OK
1.
0.059 s
OK
2.
0.059 s
OK
3.
0.058 s
OK
4.
0.057 s
OK
5.
0.058 s
OK
expand all
Performance tests
1.
0.070 s
OK
2.
0.059 s
OK
3.
0.061 s
OK
1.
0.061 s
OK
2.
0.059 s
OK
3.
0.056 s
OK
1.
0.066 s
OK
multiple_full_binary_trees
sequence of full trees of the form T=(TT), depths [1..10..1], with/without some brackets at the end, length=49K+
sequence of full trees of the form T=(TT), depths [1..10..1], with/without some brackets at the end, length=49K+
✔
OK
1.
0.062 s
OK
2.
0.059 s
OK
3.
0.062 s
OK
4.
0.061 s
OK
5.
0.061 s
OK
broad_tree_with_deep_paths
string of the form [TTT...T] of 300 T's, each T being '{{{...}}}' nested 200-fold, length=120K+
string of the form [TTT...T] of 300 T's, each T being '{{{...}}}' nested 200-fold, length=120K+
✔
OK
1.
0.064 s
OK
2.
0.065 s
OK