剑指 Offer 48. 最长不含重复字符的子字符串https://leetcode.cn/problems/zui-chang-bu-han-zhong-fu-zi-fu-de-zi-zi-fu-chuan-lcof/

dp

注意：缩小 不含重复字符子串 时的写法

dp_1 = min(i - charToIndex[s[i]], dp_0 + 1);

int lengthOfLongestSubstring(string s) {

	int n = s.size();

	// base case
	if (n < 2)
	{
		return n;
	}

	unordered_map<char, int> charToIndex;

	int dp_0 = 1;
	int dp_1 = 1;
	charToIndex.insert({ s[0],0 });

	int res = 1;
	for (int i = 1; i < n; ++i)
	{
		if (charToIndex.count(s[i]))
		{
			dp_1 = min(i - charToIndex[s[i]], dp_0 + 1);
			charToIndex[s[i]] = i;
		}
		else
		{
			dp_1 = dp_0 + 1;
			charToIndex.insert({ s[i],i });
		}

		dp_0 = dp_1;
		res = max(res, dp_1);
	}

	return res;
}