【剑指】45.把数组排成最小的数

题目描述

• 输入一个正整数数组，把数组里所有数字拼接起来排成一个数，打印能拼接出的所有数字中最小的一个。例如输入数组{3, 32, 321}，则打印出这3个数字能排成的最小数字321323。

算法分析

• 先排序， 排序规则如下：

1. 若ab > ba 则 a > b；
2. 若ab < ba 则 a < b；
3. 若ab = ba 则 a = b。
   

提交代码：

class Solution {
public:
	string PrintMinNumber(vector<int> numbers) {
		if (numbers.empty())
			return string();
		
		QuickSort(numbers, 0, numbers.size() - 1);
		string result;
		for (int each : numbers)
			result += to_string(each);

		return result;
	}

	/* 快速排序 */
	void QuickSort(vector<int> &numbers, int start, int end)
	{
		if (start < end)
		{
			int index = Partition(numbers, start, end);

			QuickSort(numbers, start, index - 1);
			QuickSort(numbers, index + 1, end);
		}
	}

	int Partition(vector<int> &numbers, int start, int end)
	{
		int pivotalkey = numbers[0];
		while (start < end)
		{
			while (start < end && newCompare(pivotalkey, numbers[end]))
				--end;
			swap(numbers[start], numbers[end]);
			while (start < end && newCompare(numbers[start], pivotalkey))
				++start;
			swap(numbers[start], numbers[end]);
		}

		return start;
	}

	/* 比较方法 */
	bool newCompare(int left, int right)
	{
		string leftString =  to_string(left);
		string rightString = to_string(right);

		string s1 = leftString + rightString;
		string s2 = rightString + leftString;

		return s1 <= s2;
	}
};

测试代码：

// ====================测试代码====================
void Test(const char* testName, vector<int> numbers, const char* expectedResult)
{
	if (testName != nullptr)
		printf("%s begins:\n", testName);

	if (expectedResult != nullptr)
		printf("Expected result is: \t%s\n", expectedResult);

	Solution s;
	printf("Actual result is: \t");
	string result = s.PrintMinNumber(numbers);
	cout << result << endl;
}

void Test1()
{
	vector<int> numbers = { 3, 5, 1, 4, 2 };
	Test("Test1", numbers, "12345");
}

void Test2()
{
	vector<int> numbers = { 3, 32, 321 };
	Test("Test2", numbers, "321323");
}

void Test3()
{
	vector<int> numbers = { 3, 323, 32123 };
	Test("Test3", numbers, "321233233");
}

void Test4()
{
	vector<int> numbers = { 1, 11, 111 };
	Test("Test4", numbers, "111111");
}

// 数组中只有一个数字
void Test5()
{
	vector<int> numbers = { 321 };
	Test("Test5", numbers, "321");
}

void Test6()
{
	Test("Test6", vector<int>(), "");
}


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

	return 0;
}