查找 - 二分查找

[code]/*递归算法, bsearch_recursion.c*/
int bsearch_recursion(int array[], int low, int high, int key)
{
    int mid_index, mid_value;
    mid_index = low + (high - low) / 2;
    mid_value = array[mid_index];

    if (low < high && key != mid_value) {
        if (key > mid_value) return bsearch_recursion(array, mid_index + 1, high, key);     
        if (key < mid_value) return bsearch_recursion(array, low, mid_index - 1, key);
    } else if (key == mid_value)
        return mid_index;
    else 
        return -1;
}

/*循环算法, bsearch_loop.c*/
int bsearch_loop(int *array, int low, int high, int key)
{
    int mid_index = low + (high - low) / 2;
    int mid_value = *(array + mid_index);
    while (low < high && key != mid_value) {
        if (key > mid_value)
            low = mid_index + 1;
        if (key < mid_value)
            high = mid_index - 1;

        mid_index = low + (high - low) / 2;
        mid_value = *(array + mid_index);
    }

    return (*(array + mid_index) == key ? mid_index : -1);
}

//bsearch.cpp
bool bsearch(std::vector<int>ivec, int target)
 {
     auto begin = ivec.begin(), end = ivec.end(), 
     mid = begin + (end - begin) / 2;
     while (begin != end && *mid != target) {
         if (*mid > target)
             end = mid - 1;
         else
             begin = mid + 1;
         mid = begin + (end - begin) / 2;
     }   

     return *mid == target;
 }