Leetcode | Online Stock Span | Kotlin

devstromo · devstromo · commit 95339f4bc4c3 · 2025-06-28T20:52:47.000-03:00
diff --git a/leetcode/src/main/kotlin/com/devstromo/medium/p901/DESCRIPTION.md b/leetcode/src/main/kotlin/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/kotlin/com/devstromo/medium/p901/StockSpannerKt.kt b/leetcode/src/main/kotlin/com/devstromo/medium/p901/StockSpannerKt.kt
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+package com.devstromo.medium.p901
+
+class StockSpannerKt() {
+    private var top: NodeKt? = null
+
+    fun next(price: Int): Int {
+        val nn: NodeKt?
+        var span = 1
+        while (top != null && top!!.price <= price) {
+            span += top!!.span
+            top = top!!.next
+        }
+        nn = NodeKt(price, span)
+        nn.next = top
+        top = nn
+        return top!!.span
+    }
+
+
+    internal class NodeKt(var price: Int, var span: Int) {
+        var next: NodeKt? = null
+    }
+
+}
diff --git a/leetcode/src/test/kotlin/com/devstromo/medium/p901/StockSpannerKtUnitTest.kt b/leetcode/src/test/kotlin/com/devstromo/medium/p901/StockSpannerKtUnitTest.kt
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+package com.devstromo.medium.p901
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+
+class StockSpannerKtUnitTest {
+    @Test
+    @DisplayName("Test Online Stock Span")
+    fun testOnlineStockSpan() {
+        val stockSpanner = StockSpannerKt()
+        var 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)
+    }
+
+}
