Tasks Details
easy
1.
Nesting
Determine whether a given string of parentheses (single type) is properly nested.
Task Score
100%
Correctness
100%
Performance
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:
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 23 minutes
Notes
not defined yet
Task timeline
Code: 15:17:31 UTC,
java,
verify,
result: Failed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st;
if(S == NULL)
return 1;
for(int i=0; i<S.length;i++){
if(S.charAt(i) == '(')
st.push（'(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Compile error
Solution.java:15: error: illegal character: '\uff08'
st.push?'(');
^
Solution.java:15: error: not a statement
st.push?'(');
^
Solution.java:16: error: 'else' without 'if'
else if(S.charAt(i) == ')' && !st.empty())
^
3 errors
Code: 15:22:17 UTC,
java,
verify,
result: Failed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st;
if(S == NULL)
return 1;
for(int i=0; i<S.length;i++){
if(S.charAt(i) == '(')
st.push（new Character('('));
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Compile error
Solution.java:15: error: illegal character: '\uff08'
st.push?new Character('('));
^
Solution.java:15: error: not a statement
st.push?new Character('('));
^
Solution.java:15: error: ';' expected
st.push?new Character('('));
^
Solution.java:16: error: 'else' without 'if'
else if(S.charAt(i) == ')' && !st.empty())
^
4 errors
Code: 15:22:40 UTC,
java,
verify,
result: Failed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st;
if(S == NULL)
return 1;
for(int i=0; i<S.length;i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Compile error
Solution.java:11: error: cannot find symbol
if(S == NULL)
^
symbol: variable NULL
location: class Solution
Solution.java:13: error: cannot find symbol
for(int i=0; i<S.length;i++){
^
symbol: variable length
location: variable S of type String
2 errors
Code: 15:23:44 UTC,
java,
verify,
result: Failed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st;
if(S == null)
return 1;
for(int i=0; i<S.length;i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Compile error
Solution.java:13: error: cannot find symbol
for(int i=0; i<S.length;i++){
^
symbol: variable length
location: variable S of type String
1 error
Code: 15:24:24 UTC,
java,
verify,
result: Failed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st;
if(S == null)
return 1;
for(int i=0; i<S.length();i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Compile error
Solution.java:15: error: variable st might not have been initialized
st.push('(');
^
Solution.java:16: error: variable st might not have been initialized
else if(S.charAt(i) == ')' && !st.empty())
^
Solution.java:18: error: variable st might not have been initialized
else if(S.charAt(i) == ')' && st.empty())
^
Solution.java:21: error: variable st might not have been initialized
if(st.empty())
^
4 errors
Code: 15:24:53 UTC,
java,
verify,
result: Passed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st = new Stack<Character>();
if(S == null)
return 1;
for(int i=0; i<S.length();i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Code: 15:25:10 UTC,
java,
verify,
result: Passed
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st = new Stack<Character>();
if(S == null)
return 1;
for(int i=0; i<S.length();i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}
Analysis
Code: 15:25:23 UTC,
java,
final,
score:
100
// 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");
import java.util.Stack;
class Solution {
public int solution(String S) {
// write your code in Java SE 8
Stack<Character> st = new Stack<Character>();
if(S == null)
return 1;
for(int i=0; i<S.length();i++){
if(S.charAt(i) == '(')
st.push('(');
else if(S.charAt(i) == ')' && !st.empty())
st.pop();
else if(S.charAt(i) == ')' && st.empty())
return 0;
}
if(st.empty())
return 1;
else
return 0;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
0.034 s
OK
2.
0.044 s
OK
1.
0.070 s
OK
1.
0.411 s
OK
2.
0.097 s
OK
3.
0.051 s
OK
1.
0.057 s
OK
2.
0.067 s
OK
3.
0.068 s
OK
expand all
Performance tests
1.
0.138 s
OK
2.
0.163 s
OK
3.
0.061 s
OK
1.
0.572 s
OK
2.
0.084 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.
0.377 s
OK
2.
0.360 s
OK
3.
0.036 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.
1.629 s
OK
2.
0.036 s
OK