John takes computer security very seriously, so he has picked a very long password to secure his files. However, although the password is very strong, it is also hard to memorize.
John decides to create a new password which is easier to remember. Therefore, it must fulfill certain requirements: he wants each character (digit or letter) to appear in the new password an even number of times (possibly zero). Also, since he is so proud of his original password, he wants the new password to be a contiguous substring of the original password.
John has trouble finding such a substring. Help him by finding, for a given string, the length of the longest substring that fulfills the requirements set out above.
Write a function:
class Solution { public int solution(string S); }
that, given a non-empty string S consisting of N characters, returns the length of the longest contiguous substring (possibly empty) of string S in which every character occurs an even number of times.
For example, given S = "6daa6ccaaa6d", the function should return 8. The longest valid password taken from S is "a6ccaaa6"; it contains four letters a, and two each of the digit 6 and letter c. Any longer substring must contain either five letters a or one letter d. Given S = "abca", the function should return 0 (note that aa is not a contiguous substring of S).
Write an efficient algorithm for the following assumptions:
- the length of string S is within the range [1..100,000];
- S consists only of lowercase letters and digits.
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(string S) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int AreAllOdd(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int AreAllOdd(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = AreAllOdd(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
//tmp code
// break;
}
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = AreAllOdd(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
Compilation failed: 1 error(s), 0 warnings Solution.cs(7,8): error CS1525: Unexpected symbol `int', expecting `class', `delegate', `enum', `interface', `partial', or `struct'
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
static int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
class Solution {
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = AreAllOdd(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
static int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = AreAllOdd(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = AreAllOdd(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
Compilation failed: 3 error(s), 0 warnings Solution.cs(13,31): error CS0246: The type or namespace name `Dictionary' could not be found. Are you missing `System.Collections.Generic' using directive? Solution.cs(50,29): error CS0103: The name `password' does not exist in the current context Solution.cs(52,58): error CS0103: The name `password' does not exist in the current context
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < password.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(password.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
Compilation failed: 2 error(s), 0 warnings Solution.cs(49,29): error CS0103: The name `password' does not exist in the current context Solution.cs(51,58): error CS0103: The name `password' does not exist in the current context
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < S.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(S.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
Console.WriteLine(oddCharCount);
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < S.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(S.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
1 2 3 2 1 2 1 2 1 2 3 2 1 2 1 2 3 2 3 2 3 2 1 1 0 1 2 1 2 1 2 1 2 1 2 3 2 1 2 1 0 1 1 2 1 2 1 2 1 2 1 0 1 0 1 2 3 1 2 1 2 3 4 1 0 1 2 3 1 0 1 2 1 2 3 1 2 1
1 2 3 2 1 2 3 1 2 1
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < S.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(S.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < S.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(S.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
using System;
using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
int LongestOddSubarrayFromStart(string password)
{
var oddCharCount = 0;
var max = 0;
var charAppearances = new Dictionary<int, int>();
for (var i = 0; i < password.Length; i++)
{
var c = password[i];
if (!charAppearances.ContainsKey(c))
{
// first appearance of this negative total sum
charAppearances.Add(c, 1);
oddCharCount++;
}
else
{
charAppearances[c]++;
if(charAppearances[c] % 2 == 0)
{
oddCharCount--;
}
else
{
oddCharCount++;
}
}
// all chars are appearing odd number of times
if(oddCharCount == 0)
{
max = i + 1;
}
}
return max;
}
public int solution(string S) {
var max = 0;
for (var i = 0; i < S.Length; i++)
{
var currentMax = LongestOddSubarrayFromStart(S.Substring(i));
if(currentMax > max)
{
max = currentMax;
}
}
return max;
}
}
The following issues have been detected: timeout errors.
long blocks of same letters, N <= 100,000
running time: >6.00 sec., time limit: 0.14 sec.
most characters in substring, N <= 100,000
running time: >6.00 sec., time limit: 0.19 sec.
random strings, all characters, N <= 100,000
running time: >6.00 sec., time limit: 0.19 sec.