20240410 Finished

src/problem/mod.rs

@@ -98,3 +98,4 @@ mod p80_remove_duplicates_from_sorted_array_ii;
 mod p169_majority_element;
 mod p189_rotate_array;
 mod p121_best_time_to_buy_and_sell_stock;
+mod p122_best_time_to_buy_and_sell_stock_ii;

src/problem/p122_best_time_to_buy_and_sell_stock_ii.rs

@@ -0,0 +1,44 @@
+/**
+ * [122] Best Time to Buy and Sell Stock II
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn max_profit(prices: Vec<i32>) -> i32 {
+        let mut result = 0;
+        let mut once_buy = 0;
+        let mut min_buy = prices[0];
+
+        for i in 1..prices.len() {
+            if prices[i] > prices[i - 1] {
+                once_buy = once_buy.max(prices[i] - min_buy);
+            } else if prices[i] < prices[i - 1] {
+                result += once_buy;
+                once_buy = 0;
+                min_buy = prices[i];
+            }
+        }
+
+        if once_buy != 0 {
+            result += once_buy;
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_122() {
+        assert_eq!(7, Solution::max_profit(vec![7, 1, 5, 3, 6, 4]));
+        assert_eq!(4, Solution::max_profit(vec![1, 2, 3, 4, 5]));
+        assert_eq!(0, Solution::max_profit(vec![7, 6, 4, 3, 2, 1]));
+    }
+}