BinarySearch returning index of where it belongs - c++

Question

So i am looking to write a code to return the index that the key is or if it is not there, where it should be. what am i missing ?
min is 0, max is size - 1, buf is sorted
int binarySearch(string buf[], string key, int min, int max){
int mid;
while (max >= min){
mid = (min + max) / 2;
if (buf[mid] < key)
min = mid + 1;
else if (buf[mid] > key)
max = mid - 1;
else
return mid;
}
return min;
}

Answer 1

I had practically the same problem, so I wrote this generic code (maybe you may want to use a different namespace than std ;) ) The code below returns the an iterator to the largest element in the sequence which is smaller than or equal to val. It uses O(N log N) time for N = std::difference(first, last), assuming O(1) random access on [first ... last).
#include <iostream>
#include <vector>
#include <algorithm>
namespace std {
template<class RandomIt, class T>
RandomIt binary_locate(RandomIt first, RandomIt last, const T& val) {
if(val == *first) return first;
auto d = std::distance(first, last);
if(d==1) return first;
auto center = (first + (d/2));
if(val < *center) return binary_locate(first, center, val);
return binary_locate(center, last, val);
}
}
int main() {
std::vector<double> values = {0, 0.5, 1, 5, 7.5, 10, 12.5};
std::vector<double> tests = {0, 0.4, 0.5, 3, 7.5, 11.5, 12.5, 13};
for(double d : tests) {
auto it = std::binary_locate(values.begin(), values.end(), d);
std::cout << "found " << d << " right after index " << std::distance(values.begin(), it) << " which has value " << *it << std::endl;
}
return 0;
}
Source: http://ideone.com/X9RsFx
The code is quite generic, it accepts std::vectors, std::arrays and arrays, or any sequence that allows random access. The assumption (read precondition) is that val >= *first and that the values [first, last) are sorted, like needed for std::binary_search.
Feel free to mention bugs or malpractices that I have used.

Answer 2

int binary_srch_ret_index(ll inp[MAXSIZE], ll e, int low, int high) {
if (low > high) {
return -1;
}
int mid = (low + high) / 2;
if (e == inp[mid]) {
return mid;
}
if (e < inp[mid]) {
return binary_srch(inp, e, low, mid - 1);
} else {
return binary_srch(inp, e, mid + 1, high);
}
}

Answer 3

You searched for a character and you assumed that charaters in the buf are sorted.
If you want to search for a string use a string match pattern algorithm.
(http://en.wikipedia.org/wiki/String_searching_algorithm)
If you want to search a character or a number in an ordered array then see this:
http://www.programmingsimplified.com/c/source-code/c-program-binary-search

Answer 4

In binary search you can do value type search not reference type. If you want to search for string in string array you have to write a complex program or use has table

Answer 5

This seems to work:
#include <iostream>
#include <cassert>
int binarySearch(int buf[], int key, int min, int max);
int main()
{
int data[] = {1,2,4,6,7,9};
for(int i=0; i<6; i++)
{
int result = binarySearch(data, data[i], 0, 5);
assert(result == i);
}
assert(binarySearch(data, 3, 0, 5) == 1);
assert(binarySearch(data, 5, 0, 5) == 2);
assert(binarySearch(data, 8, 0, 5) == 4);
assert(binarySearch(data, 10, 0, 5) == 5);
return 0;
}
int binarySearch(int buf[], int key, int min, int max)
{
int mid;
while (max >= min){
mid = (min + max) / 2;
if (buf[mid] < key)
min = mid + 1;
else if (buf[mid] > key)
max = mid - 1;
else
return mid;
}
return std::min(min, max);
}