├── 1. Two_Sum.cpp
├── 20. Valid_Parenthesis.cpp
├── LICENSE
└── README.md


/1. Two_Sum.cpp:
--------------------------------------------------------------------------------
 1 | // Intuition:
 2 | // The code utilizes a brute force approach to solve the problem. It iterates through each element of the vector and checks all possible pairs of elements to find the desired sum.
 3 | 
 4 | // Approach:
 5 | // Initialize n as the size of the vector, which represents the number of elements.
 6 | // Start iterating through each element of the vector using the variable i as the index.
 7 | // For each element at index i, iterate through the remaining elements in the vector using the variable j as the index, starting from i+1.
 8 | // Check if the sum of nums[i] and nums[j] equals the target value.
 9 | // If it does, return a vector containing the indices {i, j} as the result.
10 | // If no pair is found that satisfies the condition, return an empty vector as the result.
11 | 
12 | // Complexity Analysis:
13 | // Time Complexity: The code uses nested loops to iterate through the vector, resulting in a time complexity of O(n^2),
14 | // where n is the number of elements in the vector.
15 | // Space Complexity: The space complexity is O(1) since the code only uses a constant amount of extra space to store the indices or an empty vector.
16 | // It's worth noting that this brute force approach is not the most efficient solution for the problem.
17 | // If the input vector is very large, the time complexity of O(n^2) can be quite costly. There are more optimized algorithms, like using a hash table or sorting the vector,
18 | // which can solve the problem in a more efficient manner.
19 | 
20 | 
21 | 
22 | class Solution {
23 | public:
24 |     vector<int> twoSum(vector<int>& nums, int target) {
25 |         int n=nums.size();
26 |         for(int i=0; i<n; i++)
27 |         {
28 |             for(int j=i+1; j<n; j++)
29 |             {
30 |                 if(nums[i]+nums[j]==target)
31 |                 {
32 |                     return{i,j};
33 |                 }
34 |             }
35 |         }
36 |     return {};
37 |     }
38 | };
39 | 


--------------------------------------------------------------------------------
/20. Valid_Parenthesis.cpp:
--------------------------------------------------------------------------------
 1 | // Intuition
 2 | // The code uses a stack data structure to determine whether a given string s contains valid parentheses. 
 3 | // It iterates through each character in the string and performs the following operations:
 4 | // 1) If an opening parenthesis is encountered, it is pushed onto the stack.
 5 | // 2) If a closing parenthesis is encountered, it checks whether it matches the top element of the stack (i.e., they form a valid pair). If they do, the top element is popped from the stack. If they don't match, the closing parenthesis is pushed onto the stack.
 6 | // 3) After processing all characters, if the stack is empty, it means all opening parentheses have been matched and canceled out, resulting in a valid string.
 7 | 
 8 | // Approach
 9 | // Initialize an integer array stack of size 10000 and an integer variable top to -1 to represent an empty stack.
10 | // Get the length of the input string s and store it in the variable n.
11 | // Iterate through each character in the string using a loop.
12 | // If the stack is empty (indicated by top==-1), push the current character onto the stack by incrementing top and assigning s[i] to stack[top].
13 | // If the stack is not empty and the current character matches the closing parenthesis for the top element of the stack, pop the top element by decrementing top.
14 | // If the stack is not empty and the current character does not match the closing parenthesis for the top element of the stack, push the current character onto the stack by incrementing top and assigning s[i] to stack[top].
15 | // After processing all characters in the string, check if the stack is empty (i.e., top==-1). If it is empty, return true to indicate a valid string. Otherwise, return false.
16 | 
17 | // Complexity
18 | // Time complexity:
19 | // The code iterates through each character in the string once, resulting in a time complexity of O(n), where n is the length of the string.
20 | // Space complexity:
21 | // The code uses an integer array stack of fixed size 10000 to store the opening parentheses. Therefore, the space complexity is O(1) as the stack size remains constant regardless of the input string length.
22 | 
23 | // Code
24 | class Solution {
25 | public:
26 |     bool isValid(string s) {
27 |         int stack[10000];
28 |         int n=s.length();
29 |         int top=-1;
30 |         for(int i=0; i<n; i++)
31 |         {
32 |             if(top==-1)
33 |             {
34 |                 stack[++top]=s[i];
35 |             }
36 |             else if(stack[top]=='(' && s[i]==')' || stack[top]=='[' && s[i]==']' || stack[top]=='{' && s[i]=='}')
37 |             {
38 |                 stack[top--];
39 |             }
40 |             else
41 |             {
42 |                 stack[++top]=s[i];
43 |             }
44 |         }
45 |         if(top==-1)
46 |         {
47 |             return true;
48 |         }
49 |         else{
50 |             return false;
51 |         }
52 |     }
53 | };
54 | 


--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
 1 | MIT License
 2 | 
 3 | Copyright (c) 2023 Praful Deepak Desai
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
 1 | # Leetcode_Solutions
 2 | Welcome to the comprehensive repository designed to enhance your problem-solving abilities and assist in your preparation for technical interviews. 
 3 | This repository houses a diverse collection of efficient solutions to coding challenges from LeetCode—an esteemed platform renowned for its interview-style questions.
 4 | 
 5 | Within this repository, you will discover a wide range of meticulously crafted solutions, covering an extensive array of coding challenges.
 6 | Each solution is carefully designed to demonstrate effective problem-solving techniques, optimized algorithms, and clean code practices.
 7 | By exploring these solutions, you will gain valuable insights into various problem domains, ranging from array manipulation, string manipulation, and dynamic programming to graph traversal, tree algorithms, and more.
 8 | 
 9 | The solutions provided in this repository serve as valuable learning resources for programmers at all levels of expertise.
10 | Whether you are a beginner aiming to strengthen your problem-solving skills or an experienced developer seeking to refine your approach, these solutions offer a wealth of knowledge and guidance. 
11 | Each solution is accompanied by detailed explanations, step-by-step walkthroughs, and insights into the underlying algorithms and data structures employed.
12 | 
13 | Beyond the solutions themselves, this repository also serves as a platform for fostering a community of like-minded individuals passionate about problem-solving and technical interviews.
14 | Through discussions, code reviews, and collaboration, you can engage with fellow programmers, share your insights, and gain new perspectives on tackling coding challenges effectively.
15 | 
16 | By exploring the solutions in this repository and actively participating in the community, you will not only improve your problem-solving abilities but also enhance your familiarity with common interview-style questions.
17 | You will become adept at recognizing problem patterns, understanding algorithmic approaches, and developing efficient solutions within time constraints—a crucial skillset for excelling in technical interviews.
18 | 
19 | Feel free to navigate through the repository, explore different coding challenges, and adapt the solutions to suit your learning objectives.
20 | Engage in discussions, seek feedback on your own solutions, and embrace the opportunity to grow alongside a community of motivated programmers.
21 | Remember, consistent practice, continuous learning, and a solid understanding of algorithmic principles are key to excelling in coding challenges and technical interviews.
22 | 
23 | Harness the power of this repository, and embark on a transformative journey toward mastering problem-solving and conquering technical interviews.
24 | 


--------------------------------------------------------------------------------