Binary search to find an integer from a vector

Description

Demo Code

                                                                                                                                                                                                                          
#include <vector>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
class BinarySearch {
 public:/*  www.  jav a  2  s  . c o  m*/
    BinarySearch(int);             // constructor initializes vector
    int binarySearch(int) const;   // perform a binary search on vector
    void displayElements() const;  // display vector elements
                                                                                                                                                                                                                          
 private:
    int size;
    std::vector<int> data;
                                                                                                                                                                                                                          
    void displaySubElements(int, int) const;  // display range of values
};
                                                                                                                                                                                                                          
BinarySearch::BinarySearch(int vectorSize) {
    size = (vectorSize > 0 ? vectorSize : 10);  // validate vectorSize
    srand(time(0));
                                                                                                                                                                                                                          
    // fill vector with random ints in range 10-99
    for (int i = 0; i < size; ++i) data.push_back(10 + rand() % 90);  // 10-99
                                                                                                                                                                                                                          
    std::sort(data.begin(), data.end());
}
int BinarySearch::binarySearch(int searchElement) const {
    int low = 0;
    int high = size - 1;
    int middle = (low + high + 1) / 2;
    int location = -1;
                                                                                                                                                                                                                          
    do {
        // print remaining elements of vector to be searched
        displaySubElements(low, high);
                                                                                                                                                                                                                          
        // output spaces for alignment
        for (int i = 0; i < middle; ++i) std::cout << "  ";
                                                                                                                                                                                                                          
        std::cout << " * " << std::endl;  // indicate current middle
                                                                                                                                                                                                                          
        // if the element is found at the middle
        if (searchElement == data[middle])
            location = middle;
        else if (searchElement < data[middle])
            high = middle - 1;
        else
            low = middle + 1;
                                                                                                                                                                                                                          
        middle = (low + high + 1) / 2;  // recalculate the middle
    } while ((low <= high) && (location == -1));
                                                                                                                                                                                                                          
    return location;
}
void BinarySearch::displayElements() const { displaySubElements(0, size - 1); }
void BinarySearch::displaySubElements(int low, int high) const {
    // output alignment spaces
    for (int i = 0; i < low; ++i) std::cout << "  ";
                                                                                                                                                                                                                          
    // output elements left in vector
    for (int i = low; i <= high; ++i) std::cout << data[i] << " ";
                                                                                                                                                                                                                          
    std::cout << std::endl;
}
int main(int argc, const char* argv[]) {
    int searchInt;
    int position;
                                                                                                                                                                                                                          
    // create vector and output it
    BinarySearch searchVector(15);
    searchVector.displayElements();
                                                                                                                                                                                                                          
    // get input from user
    std::cout << "\nPlease enter an integer value (-1 to quit): ";
    std::cin >> searchInt;
    std::cout << std::endl;
                                                                                                                                                                                                                          
    // repeatedly input an integer: -1 terminates the program
    while (searchInt != -1) {
        // use binary search to try to find integer
        position = searchVector.binarySearch(searchInt);
                                                                                                                                                                                                                          
        // return value of -1 indicates integer was not found
        if (position == -1)
            std::cout << "The integer " << searchInt << " was not found.\n";
        else
            std::cout << "The integer " << searchInt
                      << " was found in position " << position << ".\n";
                                                                                                                                                                                                                          
        // get input from user
        std::cout << "\n\nPlease enter an integer value (-1 to quit): ";
        std::cin >> searchInt;
        std::cout << std::endl;
    }
                                                                                                                                                                                                                          
    return 0;
}
Binary search to find an integer from a vector - C++ STL

Description

Demo Code

Result

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