Lexicographical Maximum substring of string

Given a string s we have to find the lexicographical maximum substring of a string

Examples:

Input : s = "ababaa"
Output : babaa
Explanation : "babaa" is the maximum lexicographic susbtring formed from this string

Input : s = "asdfaa"
Output : sdfaa

The idea is simple, we traverse through all substrings. For every substring, we compare it with current result and update result if needed.

[sourcecode language=”CPP”]
// CPP program to find the lexicographically
// maximum substring.
#include <bits/stdc++.h>
using namespace std;

string LexicographicalMaxString(string str)
{
// loop to find the max leicographic
// substring in the substring array
string mx = "";
for (int i = 0; i < str.length(); ++i)
mx = max(mx, str.substr(i));

return mx;
}

int main()
{
string str = "ababaa";
cout << LexicographicalMaxString(str);
return 0;
}
[/sourcecode]

Output:

babaa

Time Complexity : O(n)
Space Complexity : O(n)

Optimization :
We find largest character and all its indexes. Now we simply traverse through all instances of the largest character to find lexicographically maximum substring.



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