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MissingNumber.cpp
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120 lines (102 loc) · 2.77 KB
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/*******************************************************************
Copyright(c) 2016, Harry He
All rights reserved.
Distributed under the BSD license.
(See accompanying file LICENSE.txt at
https://github.com/zhedahht/CodingInterviewChinese2/blob/master/LICENSE.txt)
*******************************************************************/
//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》代码
// 作者：何海涛
//==================================================================
// 面试题53（二）：0到n-1中缺失的数字
// 题目：一个长度为n-1的递增排序数组中的所有数字都是唯一的，并且每个数字
// 都在范围0到n-1之内。在范围0到n-1的n个数字中有且只有一个数字不在该数组
// 中，请找出这个数字。
#include <cstdio>
int GetMissingNumber(const int* numbers, int length)
{
if(numbers == nullptr || length <= 0)
return -1;
int left = 0;
int right = length - 1;
while(left <= right)
{
int middle = (right + left) >> 1;
if(numbers[middle] != middle)
{
if(middle == 0 || numbers[middle - 1] == middle - 1)
return middle;
right = middle - 1;
}
else
left = middle + 1;
}
if(left == length)
return length;
// 无效的输入，比如数组不是按要求排序的，
// 或者有数字不在0到n-1范围之内
return -1;
}
// ====================测试代码====================
void Test(const char* testName, int numbers[], int length, int expected)
{
if(testName != nullptr)
printf("%s begins: ", testName);
int result = GetMissingNumber(numbers, length);
if(result == expected)
printf("Passed.\n");
else
printf("Failed.\n");
}
// 缺失的是第一个数字0
void Test1()
{
int numbers[] = { 1, 2, 3, 4, 5 };
int expected = 0;
Test("Test1", numbers, sizeof(numbers) / sizeof(int), expected);
}
// 缺失的是最后一个数字
void Test2()
{
int numbers[] = { 0, 1, 2, 3, 4 };
int expected = 5;
Test("Test2", numbers, sizeof(numbers) / sizeof(int), expected);
}
// 缺失的是中间某个数字0
void Test3()
{
int numbers[] = { 0, 1, 2, 4, 5 };
int expected = 3;
Test("Test3", numbers, sizeof(numbers) / sizeof(int), expected);
}
// 数组中只有一个数字，缺失的是第一个数字0
void Test4()
{
int numbers[] = { 1 };
int expected = 0;
Test("Test4", numbers, sizeof(numbers) / sizeof(int), expected);
}
// 数组中只有一个数字，缺失的是最后一个数字1
void Test5()
{
int numbers[] = { 0 };
int expected = 1;
Test("Test5", numbers, sizeof(numbers) / sizeof(int), expected);
}
// 空数组
void Test6()
{
int expected = -1;
Test("Test6", nullptr, 0, expected);
}
int main(int argc, char* argv[])
{
Test1();
Test2();
Test3();
Test4();
Test5();
Test6();
return 0;
}