在牛客上看到這樣一道題：

題目描述

function GetNumberOfK(data, k)
{
    // write code here
    var l = 0,r = data.length,mid;
    while(l < r){
        mid = Math.floor((l+r)/2);
        if(data[mid] < k ){
            while(data[mid] == data[mid+1]){
                mid++;
            }
            l = ++mid;
        }else if(data[mid] > k){
            while(data[mid] == data[mid-1]){
                mid--;
            }
            r = --mid;
        }else{
            var sign1 = mid,sign2 = mid;
            while(sign1 <= r && data[sign1] == data[sign1+1]){
                sign1++;
            }
            while(sign2 >= l && data[sign2] == data[sign2-1]){
                sign2--;
            }
            return sign1-sign2+1;
        }
    }
    return 0;
}
module.exports = {
    GetNumberOfK : GetNumberOfK
};