add Best Time to Buy and Sell Stock solution

Author: HoonDongKang

best-time-to-buy-and-sell-stock/HoonDongKang.ts

@@ -0,0 +1,40 @@
+/**
+ * [Problem]: [121] Best Time to Buy and Sell Stock
+ *
+ * (https://leetcode.com/problems/best-time-to-buy-and-sell-stock/description/)
+ */
+function maxProfit(prices: number[]): number {
+    //시간복잡도: O(n^2);
+    //공간복잡도: O(1);
+    // Time Limit Exceeded
+    function doublyLoopFunc(prices: number[]): number {
+        let result = 0;
+        for (let i = 0; i < prices.length; i++) {
+            for (let j = i + 1; j < prices.length; j++) {
+                let profit = prices[j] - prices[i];
+                result = Math.max(profit, result);
+            }
+        }
+
+        return result;
+    }
+
+    // 시간 복잡도: O(n)
+    // 공간 복잡도: O(1)
+    function twoPointerFunc(prices: number[]): number {
+        let minPrice = prices[0];
+        let maxProfit = 0;
+
+        for (let i = 1; i < prices.length; i++) {
+            if (prices[i] < minPrice) {
+                minPrice = prices[i];
+            } else {
+                maxProfit = Math.max(maxProfit, prices[i] - minPrice);
+            }
+        }
+
+        return maxProfit;
+    }
+
+    return twoPointerFunc(prices);
+}