【整理】剑指offer——C++ 面试题3_2：数组中重复的数字

面试题3：不修改数组找出重复的数字
题目：在一个长度为n+1的数组里的所有数字都在1到n的范围内，所以数组中至少有一个数字是重复的。请找出数组中任意一个重复的数字，但不能修改输入的数组。例如，如果输入长度为8的数组{2, 3, 5, 4, 3, 2, 6, 7}，那么对应的输出是重复的数字2或者3。

#include<cstdio>
#include<iostream>

// ====================找重复数字====================
int countrage(int* number, int length, int start, int middle){
	if (number == nullptr || length < 0)
		return 0;

	int count = 0;
	for (int i = 0; i < length; i++){
		if (number[i] >= start && number[i] <= middle)
			++count;
	}
}

int getDuplication(int* numbers, int Length){
	if (numbers == nullptr || Length == 0)
	{
		return -1;
	}
	int start = 1;
	int end = Length - 1;
	while (start <= end)
	{
		int middle = ((end - start) >> 1) + start;
		int count = countrage(numbers, Length, start, middle);
		if (end == start)
		{
			if (count > 1)
				return start;
			else
				break;
		}	

		if (count > (middle - start + 1))
			end = middle;
		else
			start = middle + 1;
	}
	return -1;	
}


// ====================测试====================
void test(const char* testname, int* numbers, int Length, int* duplications, int dupLength){
	int result = getDuplication(numbers, Length);
	for (int i = 0; i < dupLength; ++i)
	{
		if (result == duplications[i])
		{
			std::cout << testname << " passed." << std::endl;
			return;
		}
	}
	std::cout << testname << " FAILED." << std::endl;
}

void test1(){
	int a,b;
	int numbers[] = { 2, 3, 5, 4, 3, 2, 6, 7 };
	int duplications[] = {2, 3};
	test("test1", numbers, sizeof(numbers)/sizeof(int), duplications, sizeof(duplications)/sizeof(int));
}

void main(){
	test1();
}