Leetcode | Online Stock Span | Java

devstromo · devstromo · commit 1dc966d0cb61 · 2025-06-28T20:05:27.000-03:00
diff --git a/leetcode/src/main/java/com/devstromo/medium/p901/DESCRIPTION.md b/leetcode/src/main/java/com/devstromo/medium/p901/DESCRIPTION.md
@@ -0,0 +1,43 @@
+# 901. Online Stock Span
+
+Design an algorithm that collects daily price quotes for some stock and returns the span of that stock's price for the
+current day.
+
+The span of the stock's price in one day is the maximum number of consecutive days (starting from that day and going
+backward) for which the stock price was less than or equal to the price of that day.
+
+- For example, if the prices of the stock in the last four days is `[7,2,1,2]` and the price of the stock today is `2`,
+  then the span of today is `4` because starting from today, the price of the stock was less than or equal `2` for `4`
+  consecutive days.
+- Also, if the prices of the stock in the last four days is `[7,34,1,2]` and the price of the stock today is `8`, then
+  the span of today is `3` because starting from today, the price of the stock was less than or equal `8` for `3`
+  consecutive days.
+
+Implement the StockSpanner class:
+
+- `StockSpanner()` Initializes the object of the class.
+- `int next(int price)` Returns the span of the stock's price given that today's price is `price`.
+
+Example 1:
+
+Input
+["StockSpanner", "next", "next", "next", "next", "next", "next", "next"]
+[[], [100], [80], [60], [70], [60], [75], [85]]
+Output
+[null, 1, 1, 1, 2, 1, 4, 6]
+
+Explanation
+StockSpanner stockSpanner = new StockSpanner();
+stockSpanner.next(100); // return 1
+stockSpanner.next(80); // return 1
+stockSpanner.next(60); // return 1
+stockSpanner.next(70); // return 2
+stockSpanner.next(60); // return 1
+stockSpanner.next(75); // return 4, because the last 4 prices (including today's price of 75) were less than or equal to
+today's price.
+stockSpanner.next(85); // return 6
+
+Constraints:
+
+- `1 <= price <= 10^5`
+- At most `10^4` calls will be made to `next`.
diff --git a/leetcode/src/main/java/com/devstromo/medium/p901/StockSpanner.java b/leetcode/src/main/java/com/devstromo/medium/p901/StockSpanner.java
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+package com.devstromo.medium.p901;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class StockSpanner {
+    private final List<Integer> list;
+
+    public StockSpanner() {
+        this.list = new ArrayList<>();
+    }
+
+    public int next(int price) {
+        list.add(price);
+        int count = 0;
+        for (int i = list.size() - 1; i >= 0; i--) {
+            if (list.get(i) <= price) {
+                count++;
+            } else {
+                break;
+            }
+        }
+        return count;
+    }
+}
diff --git a/leetcode/src/test/java/com/devstromo/medium/p901/StockSpannerUnitTest.java b/leetcode/src/test/java/com/devstromo/medium/p901/StockSpannerUnitTest.java
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+package com.devstromo.medium.p901;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class StockSpannerUnitTest {
+
+    @Test
+    @DisplayName("Test Online Stock Span")
+    void testOnlineStockSpan() {
+        StockSpanner stockSpanner = new StockSpanner();
+        int result = 0;
+        result = stockSpanner.next(100); // return 1
+        assertEquals(1, result);
+        result = stockSpanner.next(80);  // return 1
+        assertEquals(1, result);
+        result = stockSpanner.next(60);  // return 1
+        assertEquals(1, result);
+        result = stockSpanner.next(70);  // return 2
+        assertEquals(2, result);
+        result = stockSpanner.next(60);  // return 1
+        assertEquals(1, result);
+        result = stockSpanner.next(75);  // return 4, because the last 4 prices (including today's price of 75) were less than or equal to today's price.
+        assertEquals(4, result);
+        result = stockSpanner.next(85);  // return 6
+        assertEquals(6, result);
+    }
+}
