题解 | #正则表达式匹配#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param str string字符串
     * @param pattern string字符串
     * @return bool布尔型
     */
    public boolean match (String str, String pattern) {
        // write code here
        if (str == null || pattern == null || str.length() < 1 ||
                pattern.length() < 1) {
            return false;
        }
        char[] arr1 = str.toCharArray();
        char[] arr2 = pattern.toCharArray();
        int n = arr1.length;
        int m = arr2.length;
        boolean[][] dp = new boolean[n + 1][m + 1];
        dp[0][0] = true;
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j <= m; j++) {
                if (j == 0) {
                    dp[i][j] = i == 0 ? true : false;
                } else {
                    if (arr2[j - 1] != '*') {
                        if (i >= 1 && (arr1[i - 1] == arr2[j - 1] || arr2[j - 1] == '.')) {
                            dp[i][j] |= dp[i - 1][j - 1];
                        }
                    } else {
                        if (j >= 2) {
                            dp[i][j] |= dp[i][j - 2];
                        }
                        if (i >= 1 && j >= 2 && (arr1[i - 1] == arr2[j - 2] || arr2[j - 2] == '.')) {
                            dp[i][j] |= dp[i - 1][j];
                        }
                    }
                }

            }
        }
        return dp[n][m];
    }
}