@@ -0,0 +1,46 @@
+/*
+3. Longest Substring Without Repeating Characters
+Medium
+
+
+Given a string s, find the length of the longest substring without repeating characters.
+
+
+
+Example 1:
+
+Input: s = "abcabcbb"
+Output: 3
+Explanation: The answer is "abc", with the length of 3.
+Example 2:
+
+Input: s = "bbbbb"
+Output: 1
+Explanation: The answer is "b", with the length of 1.
+
+*/
+
+class Solution {
+public:
+int lengthOfLongestSubstring(string s) {
+int beg=0;
+int end=0;
+unsigned long int len=0;
+set<char> st;
+while(end<s.length())
+{
+if(!(st.count(s[end])))
+{
+st.insert(s[end]);
+len=max(st.size(),len);
+end++;
+}
+else
+{
+st.erase(s[beg]);
+beg++;
+}
+}
+return len;
+}
+};

@@ -0,0 +1,57 @@
+/*
+42. Trapping Rain Water
+Hard
+
+Example 1:
+
+
+Input: height = [0,1,0,2,1,0,1,3,2,1,2,1]
+Output: 6
+Explanation: The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped.
+Example 2:
+
+Input: height = [4,2,0,3,2,5]
+Output: 9
+
+*/
+
+class Solution {
+public:
+int trap(vector<int>& height) {
+if(height.size()==0)
+return 0;
+int i,pi=0,wt=0,s=(int)(height.size()-1),tp=0;
+int p=height[0];
+for(i=1;i<=s;i++)
+{
+if(height[i]>p)
+{
+pi=i;
+p=height[i];
+tp=0;
+}
+else
+{
+wt+=p-height[i];
+tp+=p-height[i];
+}
+}
+if(pi<s)
+{
+wt-=tp;
+p=height[s];
+for(i=s-1;i>=pi;i--)
+{
+if(height[i] >= p)
+{
+p = height[i];
+}
+else
+{
+wt += p - height[i];
+}
+}
+}
+return wt;
+}
+};

@@ -29,3 +29,5 @@
 
 **Caitlin Genna** --> "CS Computer Science Graduate, Fordham University." --> [caitlingenna](https://.com/caitlingenna)
 
+**Utkarsh Nigam** --> "Learner | C.S undergrad" --> [utkarsh-7](https://.com/utkarsh-7)
+