Tasks Details
easy
Find a symmetry point of a string, if any.
Task Score
100%
Correctness
100%
Performance
100%
Write a function:
class Solution { public int solution(String S); }
that, given a string S, returns the index (counting from 0) of a character such that the part of the string to the left of that character is a reversal of the part of the string to its right. The function should return −1 if no such index exists.
Note: reversing an empty string (i.e. a string whose length is zero) gives an empty string.
For example, given a string:
"racecar"
the function should return 3, because the substring to the left of the character "e" at index 3 is "rac", and the one to the right is "car".
Given a string:
"x"
the function should return 0, because both substrings are empty.
Write an efficient algorithm for the following assumptions:
- the length of string S is within the range [0..2,000,000].
Copyright 2009–2024 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Java 8
Time spent on task 2 minutes
Notes
not defined yet
Task timeline
Code: 09:07:02 UTC,
java,
autosave
Code: 09:07:20 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
}
}
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
var mid = S.count / 2
var start = 0
var end = S.count - 1
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Code: 09:07:31 UTC,
java,
autosave
Code: 09:07:41 UTC,
swift4,
autosave
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
var mid = S.count / 2
var start = 0
var end = S.count - 1
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Code: 09:08:03 UTC,
swift4,
autosave
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
var mid = S.count / 2
var start = 0
var end = S.count - 1
let S = Array(S)
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Code: 09:08:07 UTC,
swift4,
verify,
result: Passed
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
var mid = S.count / 2
var start = 0
var end = S.count - 1
let S = Array(S)
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Analysis
Code: 09:08:19 UTC,
swift4,
verify,
result: Passed
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
let mid = S.count / 2
var start = 0
var end = S.count - 1
let S = Array(S)
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Analysis
Code: 09:08:32 UTC,
swift4,
verify,
result: Passed
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
let mid = S.count / 2
var start = 0
var end = S.count - 1
let S = Array(S)
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}
Analysis
Code: 09:08:42 UTC,
swift4,
final,
score:
100
import Foundation
import Glibc
// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")
public func solution(_ S : inout String) -> Int {
// write your code in Swift 4.2.1 (Linux)
if S.count % 2 == 0 { return -1 }
let mid = S.count / 2
var start = 0
var end = S.count - 1
let S = Array(S)
while start < mid {
if S[start] != S[end] {
return -1
}
start += 1
end -= 1
}
return mid
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(length(S))
expand all
Correctness tests
1.
0.012 s
OK
2.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
1.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
expand all
Performance tests
1.
0.028 s
OK
2.
0.028 s
OK
3.
0.012 s
OK
1.
0.028 s
OK
1.
0.048 s
OK
1.
0.196 s
OK
1.
0.196 s
OK
2.
0.196 s
OK
3.
0.012 s
OK
1.
0.404 s
OK
2.
0.376 s
OK
3.
0.380 s
OK
4.
0.248 s
OK
5.
0.248 s
OK
6.
0.380 s
OK