<p>Given a string <code>s</code>, return <em>the last substring of</em> <code>s</code> <em>in lexicographical order</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;abab&quot;
<strong>Output:</strong> &quot;bab&quot;
<strong>Explanation:</strong> The substrings are [&quot;a&quot;, &quot;ab&quot;, &quot;aba&quot;, &quot;abab&quot;, &quot;b&quot;, &quot;ba&quot;, &quot;bab&quot;]. The lexicographically maximum substring is &quot;bab&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;leetcode&quot;
<strong>Output:</strong> &quot;tcode&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 4 * 10<sup>5</sup></code></li>
	<li><code>s</code> contains only lowercase English letters.</li>
</ul>

class Solution {
public:
    string lastSubstring(string s) {
        int i1 = 0, i2 = 1;
        int n = s.size();
        int l = 0;

        while (i2 + l < n) {
            if (s[i1+l] == s[i2+l]) {
                ++l;
                continue;
            }
            
            if (s[i1+l] < s[i2+l]) {
                i1 += l+1;
                l = 0;

                if (i1 >= i2) {
                    i2 = i1 + 1;
                }
            } else {
                i2 += l+1;
                l = 0;
            }
        }

        return s.substr(i1);
    }
};
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