diff --git a/Greedy/3458.Select-K-Disjoint-Special-Substrings/3458.Select-K-Disjoint-Special-Substrings_v2.cpp b/Greedy/3458.Select-K-Disjoint-Special-Substrings/3458.Select-K-Disjoint-Special-Substrings_v2.cpp
new file mode 100644
index 000000000..1cecdda41
--- /dev/null
+++ b/Greedy/3458.Select-K-Disjoint-Special-Substrings/3458.Select-K-Disjoint-Special-Substrings_v2.cpp
@@ -0,0 +1,60 @@
+class Solution {
+public:
+ bool maxSubstringLength(string s, int k) 
+ {
+ int n = s.size(); 
+ vector<vector<int>>pos(26);
+ for (int i=0; i<n; i++) + pos[s[i]-'a'].push_back(i); + + vector<pair<int, int>>intervals;
+ for (int letter=0; letter<26; letter++) + { + if (pos[letter].empty()) continue; + int start = pos[letter][0]; + int i = start; + int far = pos[letter].back(); + + bool flag = true; + while (i<=far) + { + far = max(far, pos[s[i]-'a'].back()); + if (pos[s[i]-'a'][0]<start) + { + flag = false; + break; + } + i++; + } + if (far-start+1==n) continue; + if (flag==false) continue; + intervals.push_back({start, far}); + } + + return helper(intervals)>=k;
+ }
+
+ bool contains(pair<int,int>a, pair<int,int>b)
+ {
+ return a.first<b.first && a.second>b.second;
+ } 
+ 
+ int helper(vector<pair<int, int>> &intervals) { 
+ int n = intervals.size();
+ vector<int>check(n, 1);
+ for (int i=0; i<n; i++)
+ for (int j=0; j<n; j++)
+ {
+ if (i==j) continue;
+ if (contains(intervals[i],intervals[j]))
+ check[i] = 0;
+ if (contains(intervals[j],intervals[i]))
+ check[j] = 0;
+ }
+ int ret = 0;
+ for (int i=0; i<n; i++) ret += check[i];
+ return ret;
+ }
+
+
+};
diff --git a/Greedy/3458.Select-K-Disjoint-Special-Substrings/Readme.md b/Greedy/3458.Select-K-Disjoint-Special-Substrings/Readme.md
index a599d5957..b489c0f20 100644
--- a/Greedy/3458.Select-K-Disjoint-Special-Substrings/Readme.md
+++ b/Greedy/3458.Select-K-Disjoint-Special-Substrings/Readme.md
@@ -8,4 +8,7 @@
 
 如果推进的过程持续至指针追上了end,那么意味着[start,end]区间内的所有字母都是自包含的。
 
-我们由此可以得到最多26段自包含的区间。我们需要判断是否至少有k个区间是彼此不相交的。这就等同于`435.Non-overlapping-Intervals`. 一个常见的贪心的做法,就是将所有区间按照尾端点排序。贪心的原则就是:如果有若干个彼此相交的区间,根据规则我们最多只能取一个,那必然只会选择尾端点更靠前的,这样会留给后续更多的空间能选择不相交的区间。所以我们必然选择排序后的第一个区间,然后顺序检查后续的区间,如果与其相交的区间都舍弃;此时下一个区间就是选择的第二个区间:因为它与首区间不相交,且尾端点是剩下所有里面最靠前的。以此类推。
+我们需要判断是否至少有k个区间是彼此不相交的。这就等同于`435.Non-overlapping-Intervals`. 一个常见的贪心的做法,就是将所有区间按照尾端点排序。贪心的原则就是:如果有若干个彼此相交的区间,根据规则我们最多只能取一个,那必然只会选择尾端点更靠前的,这样会留给后续更多的空间能选择不相交的区间。所以我们必然选择排序后的第一个区间,然后顺序检查后续的区间,如果与其相交的区间都舍弃;此时下一个区间就是选择的第二个区间:因为它与首区间不相交,且尾端点是剩下所有里面最靠前的。以此类推。
+
+事实上,还有更简单的计算逻辑。我们得到的最多26段自包含的区间,要么互斥,要么互相嵌套,不可能出现部分相交的情况。分析见`1520. Maximum Number of Non-Overlapping Substrings`. 所以我们只需要两两比较,如果大的包含小的,去掉大的即可。
+
diff --git a/Readme.md b/Readme.md
index ba7baba3a..7d6b6bfb4 100644
--- a/Readme.md
+++ b/Readme.md
@@ -1437,7 +1437,6 @@
 826.Most-Profit-Assigning-Work (M) 
 [1268.Search-Suggestions-System](https://github.com/wisdompeak/LeetCode/tree/master/Trie/1268.Search-Suggestions-System) (H-) 
 [1402.Reducing-Dishes](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1402.Reducing-Dishes) (M) 
-[1520.Maximum-Number-of-Non-Overlapping-Substrings](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1520.Maximum-Number-of-Non-Overlapping-Substrings) (H-) 
 [1564.Put-Boxes-Into-the-Warehouse-I](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1564.Put-Boxes-Into-the-Warehouse-I) (M+) 
 [1665.Minimum-Initial-Energy-to-Finish-Tasks](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1665.Minimum-Initial-Energy-to-Finish-Tasks) (H-) 
 [1686.Stone-Game-VI](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1686.Stone-Game-VI) (H-) 
@@ -1478,8 +1477,10 @@
 [2983.Palindrome-Rearrangement-Queries](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/2983.Palindrome-Rearrangement-Queries) (H+) 
 [2781.Length-of-the-Longest-Valid-Substring](https://github.com/wisdompeak/LeetCode/tree/master/String/2781.Length-of-the-Longest-Valid-Substring) (H-) 
 [3394.Check-if-Grid-can-be-Cut-into-Sections](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/3394.Check-if-Grid-can-be-Cut-into-Sections) (M) 
-[2271.Maximum-White-Tiles-Covered-by-a-Carpet](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/2271.Maximum-White-Tiles-Covered-by-a-Carpet) (M+) 
-[3413.Maximum-Coins-From-K-Consecutive-Bags](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/3413.Maximum-Coins-From-K-Consecutive-Bags) (H-) 
+[2271.Maximum-White-Tiles-Covered-by-a-Carpet](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/2271.Maximum-White-Tiles-Covered-by-a-Carpet) (M+) 
+[3413.Maximum-Coins-From-K-Consecutive-Bags](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/3413.Maximum-Coins-From-K-Consecutive-Bags) (H-)
+3104.Find Longest Self-Contained Substring (TBD) 
+[1520.Maximum-Number-of-Non-Overlapping-Substrings](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/1520.Maximum-Number-of-Non-Overlapping-Substrings) (H-) 
 [3458.Select-K-Disjoint-Special-Substrings](https://github.com/wisdompeak/LeetCode/tree/master/Greedy/3458.Select-K-Disjoint-Special-Substrings) (H-) 
 * ``Constructive Problems`` 
 [324.Wiggle-Sort-II](https://github.com/wisdompeak/LeetCode/tree/master/Others/324.Wiggle-Sort-II) (H) 
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