最长回文子串（马拉车算法）

这是过了的：

inline int expand(string s, int left, int right) {
        while (left >= 0 && right < s.size() && s[left] == s[right]) {
                --left;
                ++right;
        }
        return (right - left - 2) / 2;
}
static void solve() {
        string s = "bbbbbbbbskfaaaaaaaaa";
        string tmp = "#";
        for (char c : s) { tmp += c; tmp += "#"; }
        int n = tmp.size();
        int right = 0, center = 0, start = 0, maxLen = 0;
        vector<int> p(n, 0);
        for (int i = 0; i < n; ++i) {
                if (right >= i) {
                        int minArmLen = min(right - i, p[2 * center - i]);
                        p[i] = expand(tmp, i - minArmLen, i + minArmLen);
                } else {
                        p[i] = expand(tmp, i, i);
                }
                if (i + p[i] > right) {
                        center = i;
                        right = i + p[i];
                }
                if (p[i] > maxLen) {
                        maxLen = p[i];
                        start = (i - p[i]) / 2;
                }
        }
        cout << s.substr(start, maxLen) << endl;
}

 

 

不知道为啥这个没过：

static void solve() {
        int p[100];
        int mr = 0, mc = 0, rl = 0;//int maxRight = 0, maxCenter = 0, resLen = 0;
        int st = 0;
        string bstr, str;
        bstr = "bbbbbbbbskfaaaaaaaaa";
        for (auto x:bstr) {
                str.push_back('#');
                str.push_back(x);
        }
        str.push_back('#');
        for (int i = 0; i < str.length(); ++i) {
                if (i < mr) {
                        if (p[2 * mc - i] < mr - i) {
                                p[i] = p[2 * mc - i];
                        }
                        else {
                                p[i] = mr - i;
                                while (i - p[i] >= 0 && i + p[i] < str.length() && str[i - p[i]] == str[i + p[i]])p[i]++;
                        }
                }
                else {
                        p[i] = 1;
                        while (i - p[i] >= 0 && i + p[i] < str.length() && str[i - p[i]] == str[i + p[i]])p[i]++;
                }
                if (i + p[i] > mr) { //更新
                        mr = i + p[i];
                        mc = i;
                }
                if (p[i]>rl) { //记录
                        st = (i - p[i]) / 2;
                        rl = p[i];
                }
        }
        cout << bstr.substr(st,rl) << endl;
        return;
}