feat: 1802. Maximum Value at a Given Index in a Bounded Array : 二分查找

Author: upupming

leetcode/残酷刷题/1802. Maximum Value at a Given Index in a Bounded Array.js

@@ -0,0 +1,25 @@
+/**
+ * 二分
+ * @param {number} n
+ * @param {number} index
+ * @param {number} maxSum
+ * @return {number}
+ */
+const maxValue = function (n, index, maxSum) {
+  let l = 0; let r = 1e9
+  while (l < r) {
+    const mid = l + r + 1 >> 1
+    if (valid(mid)) l = mid
+    else r = mid - 1
+  }
+  function valid (x) {
+    let sum = x
+    // 下标 0~index-1: 分布 1, 1, ..., 1..., x-2, x-1
+    const leftCnt = Math.min(index, x - 1); const leftRest = index - leftCnt
+    sum += (x - 1 + x - leftCnt) * leftCnt / 2 + leftRest
+    const rightCnt = Math.min(n - 1 - index, x - 1); const rightRest = n - 1 - index - rightCnt
+    sum += (x - 1 + x - rightCnt) * rightCnt / 2 + rightRest
+    return sum <= maxSum
+  }
+  return l
+}

leetcode/残酷刷题/README.md

@@ -140,6 +140,7 @@
 - 1235. Maximum Profit in Job Scheduling
 - 1751. Maximum Number of Events That Can Be Attended II
 - 1300. Sum of Mutated Array Closest to Target
+- 1802. Maximum Value at a Given Index in a Bounded Array
 
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