C ++二进制搜索算法像Lower_bound一样工作

Question

I do have another question following my previous -

I am creating a version of lower_bound with something like binary search. With the BinarySearch function I find a place where to insert the new item and with the for cycle I do move the rest of the array and insert the right item so I can insert it to the right position.

But the following BinarySearch function does not work properly.

Can anyone see why?

bool CReg::AddCar ( const char *name){
    CArr * tmp = new CArr(name); // an item I am going to insert
    int pos = BinarySearch(name,0,len); //len = number of items in array
    checkLen(); // whether I do have enough space to move the array right
    if (length!=0)
        for (int i = m_len; i>=pos; i-- )
            Arr[i+1] = spzArr[i];
    Arr[pos] = tmp;
    length++;
    checkLen();
    return true;
}

int BinarySearch(const char * name, int firstindex, int lastindex) {
    if (lenght == 0) return 0; //number of items in array
    if (firstindex == lastindex) return lastindex;
    int tmp = lastindex - firstindex;
    int pos = firstindex + tmp / 2; //position the new item should go to
    if (tmp % 2)++pos;
    if (lastindex == pos || firstindex == pos) return pos;
    if (strcmp(name, Arr[pos]) < 0) return BinarySearch(name, firstindex, pos - 1);
    if (strcmp(name, Arr[pos]) > 0) return BinarySearch(name, pos + 1, lastindex);
    return pos;
    }

Answer 1

A fixed version of BinarySearch

int BinarySearch(const char* name, int firstindex, int lastindex)
{
    if (firstindex == lastindex) return lastindex;
    int dist = lastindex - firstindex;
    int mid = firstindex + dist / 2; //position the new item should go to
    if (strcmp(name, Arr[mid]) < 0) return BinarySearch(name, firstindex, mid);
    if (strcmp(name, Arr[mid]) > 0) return BinarySearch(name, mid + 1, lastindex);
    return mid;
}

But you may directly use std::lower_bound :

// Assuming std::vector<std::string> Arr;

void CReg::AddCar(const std::string& name)
{
    auto it = std::lower_bound(Arr.begin(), Arr.end(), name);
    Arr.insert(it, name);
}