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
        int row = pattern.length();
        int col = str.length();
        boolean dp[][] = new boolean[row + 1][col + 1];
        dp[0][0] = true;
        for (int i = 1; i < dp[0].length; i++) {
            dp[0][i] = false;
        }
        for (int j = 1; j < dp.length; j++) {
            dp[j][0] = false;
            if (pattern.charAt(j - 1) == '*' && dp[j - 2][0] == true) {
                dp[j][0] = true;
            }
        }
        for (int i = 1; i < dp.length; i++) {
            for (int j = 1; j < dp[0].length; j++) {
                if ((pattern.charAt(i - 1) == '.' ||
                        pattern.charAt(i - 1) == str.charAt(j - 1)) && dp[i - 1][j - 1] == true) {
                    dp[i][j] = true;
                }
                if (pattern.charAt(i - 1) == '*') {
                    if (dp[i - 2][j] == true || (pattern.charAt(i - 2) == str.charAt(j - 1) ||
                                                 pattern.charAt(i - 2) == '.') && dp[i][j - 1] == true) {
                        dp[i][j] = true;
                    }
                }
            }
        }
        return dp[row][col];
    }
}