Update 1802-maximum-value-at-a-given-index-in-a-bounded-array.js

Author: everthis

1802-maximum-value-at-a-given-index-in-a-bounded-array.js

@@ -1,3 +1,33 @@
+/**
+ * @param {number} n
+ * @param {number} index
+ * @param {number} maxSum
+ * @return {number}
+ */
+const maxValue = function(n, index, maxSum) {
+  const { floor, sqrt } = Math
+  maxSum -= n
+  if(index < Math.floor(n / 2)) index = n - 1 - index
+  let left = index // number of element to the left of the index
+  let right = n - 1 - index // number of element to the right of the index
+  // the triangle area for the left side if not hitting the boundary
+  let leftSum = floor((left * (left + 1)) / 2)
+  // the triangle area for the right side if not hitting the boundary
+  let rightSum = floor((right * (right + 1)) / 2)
+  // case: perfect pyramid
+  if (maxSum <= (rightSum * 2 + right + 1)) return floor(sqrt(maxSum) + 1)
+  // case: right side hits the boundary
+  if (maxSum <= (leftSum + rightSum + (left - right) * right + left + 1)) {
+    const b = 3 + 2 * right
+    return floor((-b + sqrt(b * b - 8 * (rightSum + 1 - right * right - maxSum))) / 2) + 1 + 1
+  }
+  // case: both sides hit boundaries
+  maxSum -= (leftSum + rightSum + (left - right) * right + left + 1)
+  return left + 1 + 1 + floor(maxSum / n)
+};
+
+// another
+
 /**
  * @param {number} n
  * @param {number} index