Question

Using C/C++, implement a function to find the length of the longest substring without repeating characters for a given string. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, and the length is 3. For string “bbbbb” the longest substring is “b”, with the length of 1.You can use either character array or string class to store the string.

Answer 1

#include <iostream>

#include<algorithm>

#include<string>

using namespace std;

void lengthOfLongestSubstring(string s) {

int i = 0, max = 0, offset = -1;

int arr[256];

string substr = "";

fill_n(arr, 256, -1);

for (i = 0; i < s.length(); i++) {

int si = (int)s[i];

offset = std::max(offset, arr[si]);

max = std::max(max, i - offset);

arr[si] = i;

}

substr = s.substr(0, max);

cout <<"the longest substring without repeating letters for \""<<s<<"\" is \""<< substr<<"\" and the length is "<< max<<endl;

}

int main()

{

cout << "Enter string ";

string s;

cin >> s;

lengthOfLongestSubstring(s);

return 0;

}

//output

Enter string abcabc the longest substring without repeating letters for "abc abc. is ab Press any key to continue .. . and the length is 3