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  • 10.Regular Expression Matching

    定义一个二维的DP数组,其中dp[i][j]表示s[0,i)和p[0,j)是否match,然后有下面三种情况
    1.  P[i][j] = P[i - 1][j - 1], if p[j - 1] != '*' && (s[i - 1] == p[j - 1] || p[j - 1] == '.');
    2.  P[i][j] = P[i][j - 2], if p[j - 1] == '*' and the pattern repeats for 0 times;
    3.  P[i][j] = P[i - 1][j] && (s[i - 1] == p[j - 2] || p[j - 2] == '.'), if p[j - 1] == '*' and the pattern repeats for at least 1 times.
    
    class Solution {
    public:
        bool isMatch(string s, string p) {
            int m = s.size(), n = p.size();
            vector<vector<bool>> dp(m + 1, vector<bool>(n + 1, false));
            dp[0][0] = true;
            for (int i = 0; i <= m; ++i) {
                for (int j = 1; j <= n; ++j) {
                    if (j > 1 && p[j - 1] == '*') {
                        dp[i][j] = dp[i][j - 2] || (i > 0 && (s[i - 1] == p[j - 2] || p[j - 2] == '.') && dp[i - 1][j]);
                    } else {
                        dp[i][j] = i > 0 && dp[i - 1][j - 1] && (s[i - 1] == p[j - 1] || p[j - 1] == '.');
                    }
                }
            }
            return dp[m][n];
        }
    };
    
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  • 原文地址:https://www.cnblogs.com/smallredness/p/10671873.html
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