链接：LintCode 炼码 - 更高效的学习体验！

题解：

class Solution {
public:
    /**
     * @param s: A string 
     * @param p: A string includes "." and "*"
     * @return: A boolean
     */
    bool isMatch(string &s, string &p) {
        // write your code here
        int m = s.size();
        int n = p.size();
        if (m <= 0 && n <= 0) {
            return true;
        }
        std::vector<std::vector<int>> dp(m+1, std::vector<int>(n+1, false));
        for (int i = 0; i <= m; ++i) {
            for (int j = 0; j <= n; ++j) {
                if (i == 0 && j == 0) {
                    dp[i][j] = true;
                } else if (j == 0) {

                } else if (i > 0 && p[j-1] == '.') {
                    // 当前.匹配上字符
                    dp[i][j] |= dp[i-1][j-1];
                } else if (p[j-1] == '*') {
                    // *表示匹配0前面字符情况，s[i-1] 和p[j-3]前面匹配决定
                    dp[i][j] |= dp[i][j-2];
                    // 把s[i-1] 和 p[j-2] 判断是否匹配，当作一个整体
                    if (i > 0 && j > 1 && (p[j-2] == s[i-1] || p[j-2] == '.')) {
                        dp[i][j] |= dp[i-1][j];
                    }
                } else if (s[i-1] == p[j-1]) {
                    // 如果字符相等
                    dp[i][j] |= dp[i-1][j-1];
                }
            }
        }
        return dp[m][n];
    }
};

class Solution {
public:
    /**
     * @param s: A string 
     * @param p: A string includes "." and "*"
     * @return: A boolean
     */
    std::vector<std::vector<int>> _dp;
    bool isMatch(string &s, string &p) {
        // write your code here
        int m = s.size();
        int n = p.size();
        if (m <= 0 && n <= 0) {
            return true;
        }
        if (n <= 0) {
            return false;
        }
        _dp.resize(m, std::vector<int>(n, -1));
        return dfs(s, p, 0, 0);
    }
private:
    bool dfs(string &s, string &p, int s1, int p1) {
        if (s1 >= s.size()) {
            if (p1 >= p.size()) {
                return true;
            }
            if (p[p1] == '*' && p1 + 1 >= p.size()) {
                return true;
            }
            if (p1 + 1 < p.size() && p[p1+1] == '*') {
                if (dfs(s, p, s1, p1+2)) {
                    return true;
                }
            }
            return false;
        }
        if (_dp[s1][p1] != -1) {
            return _dp[s1][p1] == 1 ? true : false;
        }
        if (s[s1] == p[p1]) {
            if(dfs(s, p, s1+1, p1+1)) {
                _dp[s1][p1] = 1;
                return true;
            }
            if (p1 + 1 < p.size() && p[p1+1] == '*') {
                return dfs(s, p, s1+1, p1+2) || dfs(s, p, s1, p1+2);
            }
        } else if (p[p1] == '.') {
            if(dfs(s, p, s1+1, p1+1)) {
                return true;
            }
            if (p1 + 1 < p.size() && p[p1+1] == '*') {
                cout << "test" << endl;
                _dp[s1][p1] = (dfs(s, p, s1+1, p1) || dfs(s, p, s1+1, p1+2) || dfs(s, p, s1, p1+2)) == true ? 1 : 0;
                return _dp[s1][p1] == 1 ? true : false;
            }
        } else if (p[p1] == '*') {
            if (dfs(s, p, s1, p1+1)) {
                return true;
            }
            if (p1 > 0 && (s[s1] == p[p1-1] || p[p1-1] == '.')) {
                cout << "haha" << endl;
                if (dfs(s, p, s1+1, p1)) {
                    return true;
                }
                if (dfs(s, p, s1+1, p1+1)) {
                    return true;
                }
            }
        } else if (p1 + 1 < p.size() && p[p1+1] == '*') {
            //cout << "okok" << endl;
            _dp[s1][p1] = dfs(s, p, s1, p1+2) == true ? 1 : 0;
            return _dp[s1][p1] == 1 ? true : false;
        }
        _dp[s1][p1] = 0;
        return false;
    }
};

class Solution {
    public boolean isMatch(String s, String p) {
        return search(0, 0,s,p, new Boolean[s.length() + 1][p.length() + 1]);
    }
    private boolean search(int i, int j, String s, String p, Boolean[][] memo){
        if(memo[i][j] != null){
            return memo[i][j];
        }
        boolean ans;
        if(j == p.length()){
            ans = i == s.length();
        }else{
            boolean firstMatch = (i < s.length() &&
                                  (s.charAt(i) == p.charAt(j) || p.charAt(j) == '.'));
            if(j + 1 < p.length() && p.charAt(j + 1) == '*'){
                ans = (search(i,j + 2, s, p, memo) || firstMatch &&
                       search(i + 1,j, s, p, memo));
            }else{
                ans = firstMatch && search(i + 1,j + 1, s, p, memo);
            }
        }
        memo[i][j] = ans;
        return ans;
    }
}