Add LeetCode - 121 solution in C

Algorithms/Easy/121_BestTimeToBuyAndSellStock/Solution.c

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+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;
+}