Best Time to buy and sell stock solution added

Author: Vipullakum007

dsa-solutions/lc-solutions/0100-0199/0121-best-time-to-buy-sell-stock.md

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+---
+id: best-time-to-buy-sell-stock
+title: Best Time to Buy and Sell Stock Solution
+sidebar_label: 0121-Best-Time-to-Buy-and-Sell-Stock
+tags:
+  - Best Time to Buy and Sell Stock
+  - Array
+  - LeetCode
+  - Python
+  - JavaScript
+
+description: "This is a solution to the Best Time to Buy and Sell Stock problem on LeetCode."
+---
+
+In this page, we will solve the Best Time to Buy and Sell Stock problem using a two-pointer approach. We will provide the implementation of the solution in Python and JavaScript.
+
+## Problem Description
+
+You are given an array `prices` where `prices[i]` is the price of a given stock on the `i`-th day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return `0`.
+
+### Examples
+
+**Example 1:**
+
+```plaintext
+Input: prices = [7,1,5,3,6,4]
+Output: 5
+Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
+```
+
+**Example 2:**
+
+```plaintext
+Input: prices = [7,6,4,3,1]
+Output: 0
+Explanation: In this case, no transactions are done and the max profit = 0.
+```
+
+### Constraints
+
+- `1 <= prices.length <= 10^5`
+- `0 <= prices[i] <= 10^4`
+
+---
+
+## Solution for Best Time to Buy and Sell Stock Problem
+
+### Intuition and Approach
+
+The problem can be solved using a two-pointer approach where we track the minimum price to buy and the maximum profit we can achieve at each step.
+
+<Tabs>
+ <tabItem value="Two-pointer Approach" label="Two-pointer Approach">
+
+### Approach: Two-pointer
+
+We use two pointers, `left` (to buy) and `right` (to sell), and iterate through the prices array to find the maximum profit.
+
+#### Implementation
+
+```jsx live
+function BestTimeToBuyAndSellStock() {
+  const prices = [7, 1, 5, 3, 6, 4]; // Sample input
+
+  const maxProfit = function (prices) {
+    let left = 0; // Buy
+    let right = 1; // Sell
+    let max_profit = 0;
+
+    while (right < prices.length) {
+      if (prices[left] < prices[right]) {
+        let profit = prices[right] - prices[left]; // Our current profit
+        max_profit = Math.max(max_profit, profit);
+      } else {
+        left = right;
+      }
+      right++;
+    }
+
+    return max_profit;
+  };
+
+  const result = maxProfit(prices);
+  return (
+    <div>
+      <p>
+        <b>Input:</b> prices = {JSON.stringify(prices)}
+      </p>
+      <p>
+        <b>Output:</b> {result}
+      </p>
+    </div>
+  );
+}
+```
+
+#### Codes in Different Languages
+
+<Tabs>
+  <TabItem value="JavaScript" label="JavaScript" default>
+  <SolutionAuthor name="@Vipullakum007"/>
+   ```javascript
+    function maxProfit(prices) {
+      let left = 0; // Buy
+      let right = 1; // Sell
+      let max_profit = 0;
+
+      while (right < prices.length) {
+        if (prices[left] < prices[right]) {
+          let profit = prices[right] - prices[left]; // our current profit
+          max_profit = Math.max(max_profit, profit);
+        } else {
+          left = right;
+        }
+        right++;
+      }
+
+      return max_profit;
+    }
+    ```
+
+  </TabItem>
+  <TabItem value="Python" label="Python">
+  <SolutionAuthor name="@Vipullakum007"/> 
+   ```python
+    class Solution:
+        def maxProfit(self, prices: List[int]) -> int:
+            left, right = 0, 1  # Buy, Sell
+            max_profit = 0
+
+            while right < len(prices):
+                if prices[left] < prices[right]:
+                    profit = prices[right] - prices[left]  # our current profit
+                    max_profit = max(max_profit, profit)
+                else:
+                    left = right
+                right += 1
+
+            return max_profit
+    ```
+
+  </TabItem>
+  <TabItem value="Java" label="Java"> 
+  <SolutionAuthor name="@Vipullakum007"/>
+   ```java
+    class Solution {
+        public int maxProfit(int[] prices) {
+            int left = 0; // Buy
+            int right = 1; // Sell
+            int max_profit = 0;
+
+            while (right < prices.length) {
+                if (prices[left] < prices[right]) {
+                    int profit = prices[right] - prices[left]; // our current profit
+                    max_profit = Math.max(max_profit, profit);
+                } else {
+                    left = right;
+                }
+                right++;
+            }
+
+            return max_profit;
+        }
+    }
+    ```
+
+  </TabItem>
+  <TabItem value="C++" label="C++">
+  <SolutionAuthor name="@Vipullakum007"/>
+   ```cpp
+    class Solution {
+    public:
+        int maxProfit(vector<int>& prices) {
+            int left = 0; // Buy
+            int right = 1; // Sell
+            int max_profit = 0;
+
+            while (right < prices.size()) {
+                if (prices[left] < prices[right]) {
+                    int profit = prices[right] - prices[left]; // our current profit
+                    max_profit = max(max_profit, profit);
+                } else {
+                    left = right;
+                }
+                right++;
+            }
+
+            return max_profit;
+        }
+    };
+    ```
+
+  </TabItem>  
+</Tabs>
+
+#### Complexity Analysis
+
+- Time Complexity: $$O(n)$$
+- Space Complexity: $$O(1)$$
+- Where `n` is the length of the prices array.
+
+</tabItem>
+</Tabs>
+
+:::tip Note
+
+By using a two-pointer approach, we can efficiently solve the Best Time to Buy and Sell Stock problem with a linear time complexity.
+
+:::
+
+---
+
+## References
+
+- **LeetCode Problem:** [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)
+- **Solution Link:** [Best Time to Buy and Sell Stock Solution on LeetCode](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/solutions/)
+- **Authors GeeksforGeeks Profile:** [Vipul lakum](https://www.geeksforgeeks.org/user/lakumvipwjge/)
+
+---