Leetcode day1

leetcode/lc3/NoDuplicatesSS.cpp

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+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        int n =s.length();
+        vector<int>charIndex(128,-1);
+        int left = 0;
+        int maxlen =0;
+        for(int right =0;right<n;right++){
+            if(charIndex[s[right]]>=left){
+                left = charIndex[s[right]]+1;
+            }
+            charIndex[s[right]] = right;
+            maxlen = max(maxlen, right-left+1);
+        }
+        return maxlen;
+
+    }
+};

leetcode/lc3/UsingCharSet.cpp

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+class Solution{
+    public:
+        int LengthOfLongestSubString(string s){
+            int n = s.length();
+            int maxlen = 0;
+            unordered_set<char> charset;
+            int left = 0;
+
+            for(int right = 0;right<n;right++){
+                if(charset.count(s[right])==0){
+                    charset.insert(s[right]);
+                    maxlen = max(maxlen, right-left+1);
+                }while(charset.count(s[right])){
+                    charset.erase(s[left]);
+                    left++;
+                }
+            }
+            return maxlen;
+
+
+        }
+}

leetcode/lc3/notes.md

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+My first sliding window problem. 
+Sliding Window is an algorithmic technique used to process a contiguous subarray or substring by maintaining a moving window over the input, where thewindow expands and/or shrinks while traversing the data to efficiently compute results in linear time.
+
+When to use Sliding Window :
+
+>Subarray / substring problems
+
+>Problems asking for:
+
+1)longest / shortest window
+
+2)maximum / minimum sum
+
+3)unique elements in a range
+
+4)Continuous range constraints