《剑指offer》第五十三题III：数组中数值和下标相等的元素

// 面试题53（三）：数组中数值和下标相等的元素
// 题目：假设一个单调递增的数组里的每个元素都是整数并且是唯一的。请编程实
// 现一个函数找出数组中任意一个数值等于其下标的元素。例如，在数组{-3, -1,
// 1, 3, 5}中，数字3和它的下标相等。

#include <cstdio>

int GetNumberSameAsIndex(const int* numbers, int length)
{
    if (number == nullptr || length <= 0)
        return -1;

    int start = 0;
    int end = length - 1;

    while (start <= end)
    {
        int middle = (start + end) >> 1;

        if (numbers[middle] == middle)
            return middle;

        if (numbers[middle] > middle)
            end = middle - 1;
        else
            start = middle + 1;
    }
    return -1;
}

// ====================测试代码====================
void Test(const char* testName, int numbers[], int length, int expected)
{
    if(GetNumberSameAsIndex(numbers, length) == expected)
        printf("%s passed.\n", testName);
    else
        printf("%s FAILED.\n", testName);
}

void Test1()
{
    int numbers[] = { -3, -1, 1, 3, 5 };
    int expected = 3;
    Test("Test1", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test2()
{
    int numbers[] = { 0, 1, 3, 5, 6 };
    int expected = 0;
    Test("Test2", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test3()
{
    int numbers[] = { -1, 0, 1, 2, 4 };
    int expected = 4;
    Test("Test3", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test4()
{
    int numbers[] = { -1, 0, 1, 2, 5 };
    int expected = -1;
    Test("Test4", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test5()
{
    int numbers[] = { 0 };
    int expected = 0;
    Test("Test5", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test6()
{
    int numbers[] = { 10 };
    int expected = -1;
    Test("Test6", numbers, sizeof(numbers) / sizeof(int), expected);
}

void Test7()
{
    Test("Test7", nullptr, 0, -1);
}

int main(int argc, char* argv[])
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
    Test7();

    return 0;
}