Added Best Time to Buy and Sell Stock II

Author: ryanoneill

src/best_time_to_buy_and_sell_stock_ii.rs

@@ -0,0 +1,57 @@
+/// You are given an integer array `prices` where `prices[i]` is the price of a
+/// given stock on the `ith` day.
+///
+/// On each day, you may decide to buy and/or sell the stock. You can only hold
+/// at most one share of stock at any time. However, you can buy it then
+/// immediately sell it on the same day.
+///
+/// Find and return the maximum profit you can achieve.
+struct Solution;
+
+impl Solution {
+
+    pub fn max_profit(prices: Vec<i32>) -> i32 {
+        let n = prices.len();
+        let mut result = 0;
+        let mut previous = prices[0];
+
+        for i in 1..n {
+            let today = prices[i];
+            let diff = today - previous;
+            if diff > 0 {
+                result += diff;
+            }
+            previous = today;
+        }
+
+        result
+    }
+
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    #[test]
+    fn exmaple_1() {
+        let prices = vec![7,1,5,3,6,4];
+        let result = Solution::max_profit(prices);
+        assert_eq!(result, 7);
+    }
+
+    #[test]
+    fn example_2() {
+        let prices = vec![1,2,3,4,5];
+        let result = Solution::max_profit(prices);
+        assert_eq!(result, 4);
+    }
+
+    #[test]
+    fn example_3() {
+        let prices = vec![7,6,4,3,1];
+        let result = Solution::max_profit(prices);
+        assert_eq!(result, 0);
+    }
+
+}