Add LeetCode - 121 solution in C (#62)

* Add solution to LeetCode 112

* Address requested changes

* Add leetcode 1 (nlogn approach) and leetcode 167

* Address requested changes

* Fix indentation

* Add LeetCode 121 solution in C

Author: r8025n

Algorithms/Easy/121_BestTimeToBuyAndSellStock/Solution.c

@@ -0,0 +1,13 @@
+int maxProfit(int* prices, int pricesSize){
+    int answer = 0;
+    int buyingPrice = prices[0];
+    
+    for(int i = 1; i < pricesSize; i++){
+        if(prices[i] < buyingPrice)
+            buyingPrice = prices[i];
+        else if (prices[i] - buyingPrice > answer)
+            answer = prices[i] - buyingPrice;
+    }
+    
+    return answer;
+}