数字在排序数组中出现的次数

#include<iostream>
using namespace std;

int GetFirstK(int *nums, int len, int k) {
    if (nums == NULL || len <= 0)
        return -1;

    int start = 0;
    int end = len - 1;
    int mid = 0;
    while (start < end) {
        mid = start + (end - start) / 2;
        if (nums[mid] == k) {
            end = mid;
        } else if (nums[mid] < k) {
            start = mid + 1;
        } else {
            end = mid - 1;
        }
    }

    return start;
}

int GetLastK(int *nums, int len, int k) {
    if (nums == NULL || len <= 0)
        return -1;

    int start = 0;
    int end = len - 1;
    int mid = 0;
    while (start < end) {
        if (start + 1 == end) {
            if (nums[start] == nums[end]) { //防止死循环，注意
                return end;
            } else {
                return start;
            }
        }
        mid = start + (end - start) / 2;
        if (nums[mid] == k) {
            start = mid;
        } else if (nums[mid] < k) {
            start = mid + 1;
        } else {
            end = mid - 1;
        }
    }

    return end;
}

int GetNum(int *nums, int len, int k) {
    if (nums == NULL || len <= 0)
        return k;

    int start_pos = GetFirstK(nums, len, k);
    int end_pos = GetLastK(nums, len, k);

    return end_pos - start_pos + 1;
}

int main() {
    int nums[] = {1,2,3,3,3,3,4,5};
    int nums1[] = {3};
    int nums2[] = {1,3,3,3,4};
    cout<<GetNum(nums, 8, 3)<<endl;

    return 0;
}