java字符串匹配dp_字符串匹配问题

最新推荐文章于 2022-08-26 21:05:00 发布

weixin_39989668

最新推荐文章于 2022-08-26 21:05:00 发布

阅读量158

点赞数

文章标签： java字符串匹配dp

本文链接：https://blog.youkuaiyun.com/weixin_39989668/article/details/114623202

版权

本文介绍了两种实现正则表达式匹配的算法：递归解法与动态规划解法。递归方法通过逐字符对比来判断字符串是否符合正则表达式的规则；动态规划方法则利用二维数组记录中间结果，避免重复计算，提高效率。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

递归解法 import java.util.*;

public class Main {

//isValid

public static boolean isValid(char[] s, char[] e) {

for(int i = 1; i < e.length; i++) {

if (e[i] == '*' && e[i - 1] == '*')

return false;

}

return true;

}

public static boolean judge(char[] s, char[] e, int si, int ei) {

if (ei == e.length) {

return si == s.length;

}

if (ei + 1 == e.length || e[ei + 1] != '*') {

return si != s.length && (e[ei] == s[si] || e[ei] == '.')

&& judge(s, e, si + 1, ei + 1);

}

while (si != s.length && (e[ei] == s[si] || e[ei] == '.')) {

if (judge(s, e, si, ei + 2)) {

return true;

}

si ++;

}

return judge(s, e, si, ei + 2);

}

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

char[] s = sc.nextLine().toCharArray();

char[] e = sc.nextLine().toCharArray();

sc.close();

if (!isValid(s, e)) {

System.out.println("NO");

return;

}

if (!judge(s, e, 0, 0)) {

System.out.println("NO");

} else {

System.out.println("YES");

}

动态规划解法 import java.util.*;

public class Main {

public static boolean isValid(char[] s, char[] e) {

for (int i = 0; i < s.length; i++) {

if (s[i] == '*' || s[i] == '.') {

return false;

}

for (int i = 0; i < e.length; i++) {

if (e[i] == '*' && (i == 0 || e[i - 1] == '*')) {

return false;

}

return true;

}

public static boolean isMatchDP(String str, String exp) {

if (str == null || exp == null) {

return false;

}

char[] s = str.toCharArray();

char[] e = exp.toCharArray();

if (!isValid(s, e)) {

return false;

}

boolean[][] dp = initDPMap(s, e);

for (int i = s.length - 1; i > -1; i--) {

for (int j = e.length - 2; j > -1; j--) {

if(e[j + 1] != '*') {

dp[i][j] = (s[i] == e[j] || e[j] == '.') && dp[i + 1][j + 1];

} else {

int si = i;

while (si != s.length && (s[si] == e[j] || e[j] == '.')) {

if (dp[si][j + 2]) {

dp[i][j] = true;

break;

}

si++;

}

if (dp[i][j] != true) {

dp[i][j] = dp[si][j + 2];

}

return dp[0][0];

}

public static boolean[][] initDPMap(char[] s, char[] e) {

int slen = s.length;

int elen = e.length;

boolean[][] dp = new boolean[slen + 1][elen + 1];

dp[slen][elen] = true;

for (int j = elen - 2; j > -1; j -= 2) {

if (e[j] != '*' && e[j + 1] == '*') {

dp[slen][j] = true;

} else {

break;

}

if (slen > 0 && elen > 0) {

if ((e[elen - 1] == '.' || s[slen - 1] == e[elen - 1])) {

dp[slen - 1][elen - 1] = true;

}

return dp;

}

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

String str = sc.nextLine();

String exp = sc.nextLine();

if (isMatchDP(str, exp)) {

System.out.println("YES");

} else {

System.out.println("NO");

}