题解 | #包含不超过两种字符的最长子串#

#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;

int lengthOfLongestSubstringTwoDistinct(const string& s) {
    unordered_map<char, int> charCount;
    int maxLength = 0;
    int left = 0;

    for (int right = 0; right < s.length(); right++) {
        charCount[s[right]]++;  // Increment the count of the character at right

        // While we have more than two distinct characters, move the left pointer
        while (charCount.size() > 2) {
            charCount[s[left]]--;  // Decrement the count of the character at left
            if (charCount[s[left]] == 0) {
                charCount.erase(
                    s[left]);  // Remove the character completely if count goes to zero
            }
            left++;  // Move the left pointer to the right
        }

        // Calculate the current length of the substring
        maxLength = max(maxLength, right - left + 1);
    }

    return maxLength;
}

int main() {
    string input;
    cin >> input;
    cout << lengthOfLongestSubstringTwoDistinct(input) << endl;
    return 0;
}
// 64 位输出请用 printf("%lld")