// program with some examples of calling the assert macro.  When we
// uncomment the line that defines NDEBUG, the assertions are turned
// off (not even compiled).

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
// #define NDEBUG
#include <assert.h>

using namespace std;

int binary_search(const vector<int> & v, int value) {
    // the following assertion worked, but was expensive (slow)
    // assert(is_sorted(v.begin(), v.end()));
    int low = 0;
    int high = v.size() - 1;
    while (low <= high) {
        // simpler assertion that works fairly well without increasing
        // the complexity
        assert(v[low] <= v[high]);
        int mid = low + (high - low) / 2;
        if (v[mid] == value) {
            return mid;
        } else if (v[mid] < value) {
            low = mid + 1;
        } else { // v[mid] > value
            high = mid - 1;
        }
    }
    return -1;
}

// program that transfers text from s1 to s2
void transfer(string & s1, string & s2) {
    s2 = s2 + ", " + s1;
    s1 = "";
    // it seemed that this assertion would always be true because of
    // the comma added to s2, but that's not true when the function is
    // passed the same string twice
    assert(!s2.empty());
}

// program that tests binary_search by constructing a vector of given
// size, filling it up with 0 through size-1, then randomizing and
// calling binary_search again.
void test(int size) {
    vector<int> v;
    v.reserve(size);
    for (int i = 0; i < size; i++) {
        v.push_back(i);
    }
    cout << "working with vector of size " << size << endl;
    cout << "results when sorted:" << endl;
    int okay = 0;
    for (int i = 0; i < size; i++) {
        if (binary_search(v, i) == i) {
            okay++;
        }
    }
    cout << okay << " values correct" << endl;

    random_shuffle(v.begin(), v.end());
    cout << "results when shufled:" << endl;
    okay = 0;
    for (int i = 0; i < size; i++) {
        if (binary_search(v, i) == i) {
            okay++;
        }
    }
    cout << okay << " values correct" << endl;
    cout << endl;
}

int main() {
    srand (time(nullptr)); // to seed the random number generator
    // test(10000);

    string s1 = "hello";
    string s2 = "there";
    cout << "s1 = '" << s1 << "', s2 = '" << s2 << "'" << endl;
    transfer(s1, s1);
    cout << "s1 = '" << s1 << "', s2 = '" << s2 << "'" << endl;

    return 0;
}