395. Longest Substring with At Least K Repeating Characters | LeetCode Solution
Given a string s
and an integer k
, return the length of the longest substring of s
such that the frequency of each character in this substring is greater than or equal to k
.
Example 1:
Input: s = "aaabb", k = 3 Output: 3 Explanation: The longest substring is "aaa", as 'a' is repeated 3 times.
Example 2:
Input: s = "ababbc", k = 2 Output: 5 Explanation: The longest substring is "ababb", as 'a' is repeated 2 times and 'b' is repeated 3 times.
Constraints:
1 <= s.length <= 104
s
consists of only lowercase English letters.1 <= k <= 105
class Solution
{
public:
int longestSubstring(string s, int k)
{
int n = s.length();
unordered_map<char, int> mymap;
for (char c : s)
mymap[c]++;
int mid = 0;
while (mid < n && mymap[s[mid]] >= k)
mid++;
if (mid == n)
return n;
int left = longestSubstring(s.substr(0, mid), k);
while (mid < n && mymap[s[mid]] < k)
mid++;
int right = longestSubstring(s.substr(mid), k);
return max(left, right);
}
};
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