剑指offer38 数字在排序数组中出现的次数

这种方法没用迭代，而是使用了循环的方式

class Solution {
public:
int GetNumberOfK(vector<int> data ,int k) {
if(data.empty())
return 0;
int First = getFirstofK(data,k);
int Last = getLastofK(data,k);
if(First == -1 || Last == -1)
return 0;
else
return Last - First + 1;
}
int getFirstofK(vector<int> data,int k){
int length = data.size();
int begin = 0;
int end = length - 1;
while(begin <= end){
int mid = (begin + end)/2;
if(data[mid] == k){
if(data[mid-1] != k)
return mid;
else
end = mid - 1;
}
else if(data[mid] < k)
begin = mid + 1;
else
end = mid - 1;
}
return -1;
}
int getLastofK(vector<int> data,int k){
int length = data.size();
int begin = 0;
int end = length - 1;
while(begin <= end){
int mid = (begin + end)/2;
if(data[mid] == k){
if(data[mid+1] != k)
return mid;
else
begin = mid + 1;
}
else if(data[mid] < k)
begin = mid + 1;
else
end = mid - 1;
}
return -1;
}
};