Test results - Codility

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 ')'.

Solution

Programming language used Java 21

Time spent on task 23 minutes

Notes

not defined yet

Code: 15:17:31 UTC, java, verify, result: Failed

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// 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

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

expand all Example tests

▶

example1
example test

✔

0.014 s

▶

example2
example test2

✔

0.013 s

Code: 15:25:10 UTC, java, verify, result: Passed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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

expand all Example tests

▶

example1
example test

✔

0.016 s

▶

example2
example test2

✔

0.019 s

Code: 15:25:23 UTC, java, final, score: 100

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

// 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 Example tests

▶

example1
example test

✔

0.094 s

▶

example2
example test2

✔

0.039 s

expand all Correctness tests

▶

negative_match
invalid structure, but the number of parentheses matches

✔

0.034 s

0.044 s

▶

empty
empty string

✔

0.070 s

▶

simple_grouped
simple grouped positive and negative test, length=22

✔

0.411 s

0.097 s

0.051 s

▶

small_random

✔

0.057 s

0.067 s

0.068 s

expand all Performance tests

▶

large1
simple large positive and negative test, 10K or 10K+1 ('s followed by 10K )'s

✔

0.138 s

0.163 s

0.061 s

▶

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

✔

0.572 s

0.084 s

▶

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+

✔

0.377 s

0.360 s

0.036 s

▶

broad_tree_with_deep_paths
string of the form (TTT...T) of 300 T's, each T being '(((...)))' nested 200-fold, length=1 million

✔

1.629 s

0.036 s