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2774. Array Upper Bound

Description

Write code that enhances all arrays such that you can call the upperBound() method on any array and it will return the last index of a given target number. nums is a sorted ascending array of numbers that may contain duplicates. If the target number is not found in the array, return -1.

 

Example 1:

Input: nums = [3,4,5], target = 5
Output: 2
Explanation: Last index of target value is 2

Example 2:

Input: nums = [1,4,5], target = 2
Output: -1
Explanation: Because there is no digit 2 in the array, return -1.

Example 3:

Input: nums = [3,4,6,6,6,6,7], target = 6
Output: 5
Explanation: Last index of target value is 5

 

Constraints:

  • 1 <= nums.length <= 104
  • -104 <= nums[i], target <= 104
  • nums is sorted in ascending order.

Solutions

  • declare global {
        interface Array<T> {
            upperBound(target: number): number;
        }
    }
    
    Array.prototype.upperBound = function (target: number) {
        let left = 0;
        let right = this.length;
        while (left < right) {
            const mid = (left + right) >> 1;
            if (this[mid] > target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return left > 0 && this[left - 1] == target ? left - 1 : -1;
    };
    
    // [3,4,5].upperBound(5); // 2
    // [1,4,5].upperBound(2); // -1
    // [3,4,6,6,6,6,7].upperBound(6) // 5
    
    

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