std::map's lower_bound() test

std_map_lowerbound.cpp

// Test std::map's lower_bound()

#include <stdio.h>
#include <map>
#include <iostream>

struct range_t
{
    unsigned long a;
    unsigned long b;

    bool contains(unsigned long x)
    {
        return x >= a && x <= b;
    }
};

typedef std::map<unsigned long, range_t *> eud_items_lookup_t;

range_t test_items[] = 
{
    {5, 8},
    {10, 12},
    {14, 18},
    {22, 26}
};

int main()
{
    // Convert to map
    eud_items_lookup_t lookup;
    for (auto &item : test_items)
        lookup[item.a] = &item;

    auto items_end = std::end(lookup);

    unsigned long fk;

    while (true)
    {
        std::cin >> fk;
        if (fk == 0)
            break;

        // return an entry whose key is not less than the search key
        auto lb = lookup.lower_bound(fk);

        // Two cases:
        // 1. No key greater then fk
        // 2. Did not find the exact key
        if (lb == items_end || lb->second->a != fk)
        {
            // Check the previous element
            --lb;
            if (lb == items_end || !lb->second->contains(fk))
            {
                printf("not found\n");
                continue;
            }
        }

        printf("%d - %d\n",
            lb->second->a,
            lb->second->b);
    }

    return 0;
}