题解 | #数字在升序数组中出现的次数#使用迭代器做二分查找

class Solution {
public:
    int GetNumberOfK(vector<int> data ,int k) {
        auto beg = data.begin(), end = data.end();

        int num = 0;

        while (beg < end) {
            auto mid = beg + (end - beg) / 2;
            if (*mid < k) {
                beg = mid + 1;
                continue;
            }
            if (*mid > k) {
                end = mid - 1;
                continue;
            }
            if (*mid == k) {
                ++num;
                auto left = mid - 1, right = mid + 1;
                while (left >= data.begin()) {
                    if (*left != k) break;
                    ++num;
                    --left;
                }
                while (right < data.end()) {
                    if (*right != k) break;
                    ++num;
                    ++right;
                }
                break;
            }
        }

        return num;
        
    }
};