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:
function solution(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 JavaScript
Time spent on task 37 minutes
Notes
not defined yet
Code: 02:00:37 UTC,
java,
autosave
Code: 02:04:40 UTC,
js,
autosave
function solution(S) {
// write your code in JavaScript (Node.js 8.9.4)
let progress = true
let index = 0
let stack = []
let error = false
while (index < S.length) {
if (stack.length === 0) {
if (S[index] === ')' ) {
return 0
} else {
stack.push(S[index])
}
}
else if (is_properly_nested(stack[stack.length-1],S[index])) {
stack.pop(stack[stack.length-1])
} else {
if (S[index] === ')' ) {
return 0
}
else {
stack.push(S[index])
}
}
index ++
}
if (stack.length === 0) {
return 1
} else {
return 0
}
}
function is_properly_nested(a,b){
if (a === '(' && b === ')') {
return true
}
else {
return false
}
}
Code: 02:04:40 UTC,
js,
verify,
result: Passed
function solution(S) {
// write your code in JavaScript (Node.js 8.9.4)
let progress = true
let index = 0
let stack = []
let error = false
while (index < S.length) {
if (stack.length === 0) {
if (S[index] === ')' ) {
return 0
} else {
stack.push(S[index])
}
}
else if (is_properly_nested(stack[stack.length-1],S[index])) {
stack.pop(stack[stack.length-1])
} else {
if (S[index] === ')' ) {
return 0
}
else {
stack.push(S[index])
}
}
index ++
}
if (stack.length === 0) {
return 1
} else {
return 0
}
}
function is_properly_nested(a,b){
if (a === '(' && b === ')') {
return true
}
else {
return false
}
}
Analysis
Code: 02:04:44 UTC,
js,
verify,
result: Passed
function solution(S) {
// write your code in JavaScript (Node.js 8.9.4)
let progress = true
let index = 0
let stack = []
let error = false
while (index < S.length) {
if (stack.length === 0) {
if (S[index] === ')' ) {
return 0
} else {
stack.push(S[index])
}
}
else if (is_properly_nested(stack[stack.length-1],S[index])) {
stack.pop(stack[stack.length-1])
} else {
if (S[index] === ')' ) {
return 0
}
else {
stack.push(S[index])
}
}
index ++
}
if (stack.length === 0) {
return 1
} else {
return 0
}
}
function is_properly_nested(a,b){
if (a === '(' && b === ')') {
return true
}
else {
return false
}
}
Analysis
Code: 02:36:33 UTC,
js,
verify,
result: Passed
function solution(S) {
// write your code in JavaScript (Node.js 8.9.4)
let progress = true
let index = 0
let stack = []
let error = false
while (index < S.length) {
if (stack.length === 0) {
if (S[index] === ')' ) {
return 0
} else {
stack.push(S[index])
}
}
else if (is_properly_nested(stack[stack.length-1],S[index])) {
stack.pop(stack[stack.length-1])
} else {
if (S[index] === ')' ) {
return 0
}
else {
stack.push(S[index])
}
}
index ++
}
if (stack.length === 0) {
return 1
} else {
return 0
}
}
function is_properly_nested(a,b){
if (a === '(' && b === ')') {
return true
}
else {
return false
}
}
Analysis
Code: 02:36:36 UTC,
js,
final,
score: 
100
function solution(S) {
// write your code in JavaScript (Node.js 8.9.4)
let progress = true
let index = 0
let stack = []
let error = false
while (index < S.length) {
if (stack.length === 0) {
if (S[index] === ')' ) {
return 0
} else {
stack.push(S[index])
}
}
else if (is_properly_nested(stack[stack.length-1],S[index])) {
stack.pop(stack[stack.length-1])
} else {
if (S[index] === ')' ) {
return 0
}
else {
stack.push(S[index])
}
}
index ++
}
if (stack.length === 0) {
return 1
} else {
return 0
}
}
function is_properly_nested(a,b){
if (a === '(' && b === ')') {
return true
}
else {
return false
}
}
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
0.068 s
OK
2.
0.068 s
OK
1.
0.068 s
OK
1.
0.068 s
OK
2.
0.068 s
OK
3.
0.068 s
OK
1.
0.072 s
OK
2.
0.068 s
OK
3.
0.068 s
OK
expand all
Performance tests
1.
0.076 s
OK
2.
0.076 s
OK
3.
0.068 s
OK
1.
0.104 s
OK
2.
0.068 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.
0.076 s
OK
2.
0.076 s
OK
3.
0.068 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.
0.092 s
OK
2.
0.068 s
OK