Practice27:统计一个数字在升序数组中出现的次数

Practice27:

统计一个数字在升序数组中出现的次数

S1

遍历比较法

class Solution {
public:
    int GetNumberOfK(vector<int> data ,int k) {
        int res = 0;
        for(int val:data){
            if(val==k)++res;
        }
        return res;
    }
};

S2

二分法

class Solution {
public:
    int GetNumberOfK(vector<int> data ,int k) {
        int lbound=0,rbound=0;
        int l,r;
        l=0;
        r=data.size();
        while(l<r){
            int mid = l+(r-l)*0.5;
            if(data[mid]<k){
                l = mid+1;
            }
            else{
                r = mid;
            }
        }
        lbound = l;
        r = data.size();
        while(l<r){
            int mid = l+(r-l)*0.5;
            if(data[mid]<=k){
                l = mid+1;
            }
            else{
                r = mid;
            }
        }
        rbound = r;
        return rbound-lbound;
    }
};