Create 0837-new-21-game.js

Author: jaliph

javascript/0837-new-21-game.js

@@ -0,0 +1,34 @@
+/**
+ * https://leetcode.com/problems/new-21-game/
+ * @param {number} n
+ * @param {number} k
+ * @param {number} maxPts
+ * @return {number}
+ */
+var new21Game = function(n, k, maxPts) {
+  if (k == 0) {
+    return 1
+  }  
+
+  let windowSum = 0
+  for (let i = k; i < k + maxPts; i++) {
+    if (i <= n) {
+      windowSum += 1
+    }
+  }
+
+  let dp = {}
+  for (let i = k - 1; i >= 0; i--) {
+    dp[i] = windowSum / maxPts
+
+    let remove = 0
+    if (i + maxPts <= n) {
+      remove = dp[i + maxPts] || 1
+    }
+
+    windowSum += dp[i]
+    windowSum -= remove
+  }
+
+  return dp[0]
+};