[LeetCode]Reorder Log Files

这道题定义自己custom的compare function即可，按照题目的要求来。注意用stable sort因为要保持数组log的原顺序。时间复杂度O(n * log n)，代码如下：

	string getId(const string& s, int& i)
	{
	string id;
	while (s[i] == ' ')++i;
	while (s[i] != ' ')id += s[i++];
	while (s[i] == ' ')++i;
	return id;
	}
	bool compare(const string& s1, const string& s2)
	{
	int i1 = 0, i2 = 0;
	string id1 = getId(s1, i1), id2 = getId(s2, i2);
	string log1 = s1.substr(i1), log2 = s2.substr(i2);
	bool isDigit1 = isdigit(s1[i1]), isDigit2 = isdigit(s2[i2]);
	if (!isDigit1 && !isDigit2)
	{
	int comp = log1.compare(log2);
	if (!comp)
	return s1.compare(s2) < 0;
	else
	return comp < 0;
	}
	return isDigit1 ? false : true;
	}
	class Solution {
	public:
	vector<string> reorderLogFiles(vector<string>& logs) {
	stable_sort(logs.begin(), logs.end(), compare);
	return logs;
	}
	};

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