leetcode1147 段式回文

思路：

不断贪心地寻找最短公共前后缀即可。贪心法的正确性证明：https://leetcode-cn.com/problems/longest-chunked-palindrome-decomposition/solution/tan-xin-fa-zheng-que-xing-de-xiang-xi-zheng-ming-b/

实现：

class Solution
{
public:
    int dfs(string t, int l, int r)
    {
        if (l >= r) return l == r;
        int m = l + r >> 1, p = r, len = 0; 
        bool flg = false;
        while (p > m)
        {
            if (t[p] == t[l])
            {
                len = r - p + 1;
                if (t.substr(l, len) == t.substr(p, len))
                {
                    flg = true; break;
                }
            }
            p--;
        }
        if (flg) return dfs(t, l + len, r - len) + 2;
        else return 1;
    }
    int longestDecomposition(string text)
    {
        int n = text.length();
        return dfs(text, 0, n - 1);
    }
};