April Week 1 Done

122/main.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <limits.h>
+
+int maxProfit(int*, int);
+int maxProfit(int* prices, int pricesSize){
+    // Each time the direction changes buy/sell at that price if possible
+    // only make decision once past the decision point
+    // Only count profit once sold
+    int profit = 0;
+    int buy = 0; // zero will represent looking to buy, 1 will be looking to sell
+    int current_stock = -1; // This will represent the value of the current bought stock, to sell, put this into profit var
+    int last = INT_MAX; // This will be used to look back
+
+    // Apply basic strategy
+    for (int i = 0; i < pricesSize; i++) {
+        if (buy == 0 && prices[i] > last) {
+            buy = 1; // buy this stuff
+            current_stock = last;
+        } else if (buy == 1 && prices[i] < last) {
+            // sell at the last price in retrospect
+            buy = 0;
+            profit = profit + last - current_stock;
+            current_stock = -1;
+        }
+        last = prices[i];
+    }
+
+    // Need to check if we can sell at last price or not
+    // i.e. there hasn't been a swing back, it's all up baby
+    if (current_stock != -1 && last > current_stock) {
+        profit = profit + last - current_stock;
+    }
+
+    return profit; 
+}
+
+int main() {
+    int prices[6] = {7, 1, 5, 3, 6, 4};
+    printf("Expected: 7\n");
+    printf("Got: %d\n", maxProfit(prices, 6));
+    /*
+    int prices_two[5] = {1, 2, 3, 4, 5};
+    printf("Expected: 4\n");
+    printf("Got: %d\n", maxProfit(prices_two, 5));
+    int prices_three[5] = {7, 6, 4, 3, 1};
+    printf("Expected: 0\n");
+    printf("Got: %d\n", maxProfit(prices_three, 5));
+    */
+    return 0;
+}

122/problem.txt

@@ -0,0 +1,26 @@
+Say you have an array for which the ith element is the price of a given stock on day i.
+
+Design an algorithm to find the maximum profit. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).
+
+Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).
+
+Example 1:
+
+Input: [7,1,5,3,6,4]
+Output: 7
+Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
+             Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
+
+Example 2:
+
+Input: [1,2,3,4,5]
+Output: 4
+Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
+             Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are
+             engaging multiple transactions at the same time. You must sell before buying again.
+
+Example 3:
+
+Input: [7,6,4,3,1]
+Output: 0
+Explanation: In this case, no transaction is done, i.e. max profit = 0.

122/run.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+gcc -o main main.c
+./main
+rm main