diff --git a/Daily Questions/#1358 - Number of Substrings Containing All Three Characters - Medium/Explanation.md b/Daily Questions/#1358 - Number of Substrings Containing All Three Characters - Medium/Explanation.md
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+# Solution Explanation
+
+## Purpose
+The code is designed to count the number of substrings that contain all three characters 'a', 'b', and 'c' at least once.
+
+## Code Breakdown
+
+### Initialization
+```java
+HashMap<Character, Integer> freq = new HashMap<>();
+int left = 0, cnt = 0;
+
+Time complexity: O(n)
+Space complexity: O(n)
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diff --git a/Daily Questions/#1358 - Number of Substrings Containing All Three Characters - Medium/Solution.java b/Daily Questions/#1358 - Number of Substrings Containing All Three Characters - Medium/Solution.java
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+class Solution {
+    public int numberOfSubstrings(String s) {
+        HashMap<Character, Integer> freq = new HashMap<>();
+        int left = 0, cnt = 0;
+        
+        for (int i = 0; i < s.length(); i++) {
+            freq.put(s.charAt(i), freq.getOrDefault(s.charAt(i), 0) + 1);
+            
+            while (freq.size() == 3) {
+                cnt += s.length() - i;
+                freq.put(s.charAt(left), freq.get(s.charAt(left)) - 1);
+                if (freq.get(s.charAt(left)) == 0) {
+                    freq.remove(s.charAt(left));
+                }
+                left++;
+            }
+        }
+        
+        return cnt;
+    }
+}
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