剑指 Offer 53 - I. 在排序数组中查找数字 I 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
class Solution {
    public int search(int[] nums, int target) {
        return findRightBoundExclusiveIndex(nums, target) - findRightBoundExclusiveIndex(nums, target - 1);
    }

    private int findRightBoundExclusiveIndex(int[] nums, int target) {
        int left = 0, right = nums.length - 1; // [left, right]
        while (left <= right) {
            int mid = (left + right) >>> 1;
            if (nums[mid] > target) {
                right = mid - 1;
            } else if (nums[mid] < target) {
                left = mid + 1;
            } else {
                left = mid + 1;
            }
        }

        // right, left
        return left;
    }
}

References

剑指 Offer 53 - I. 在排序数组中查找数字 I