正则表达式
一种字符串压缩表示的解压
给几个用例：3bb，bbb，3b4b
import java.util.Scanner;
import java.util.*;
import java.util.regex.*;;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String s = in.nextLine();
if (Character.isDigit(s.charAt(s.length() - 1))){ // 最后一位是数字
System.out.println("!error");
return;
}
char[] chars = s.toCharArray();
for (char c : chars) {
// 不是 数字，也不是字母
if (!Character.isDigit(c) && !Character.isLowerCase(c)){
System.out.println("!error");
return;
}
}
Map<Integer, String> map = new HashMap<>();
// 正则！！！
String reg = "(\\d+)([a-zA-Z])";
Matcher matcher = Pattern.compile(reg).matcher(s);
while (matcher.find()){
StringBuilder sb = new StringBuilder();
int start = matcher.start();
int count = Integer.parseInt(matcher.group(1));
if (count > 100){ // p1r2831z38268783t9o 题中说了：字符串的长度不会超过 100
System.out.println("!error");
return;
}
for (int i = 0; i < count; i++) {
sb.append(matcher.group(2));
}
map.put(start, sb.toString());
}
StringBuilder sb = new StringBuilder();
for (int i = 0; i < chars.length; i++) {
if (map.containsKey(i)){
sb.append(map.get(i));
int count = 0;
int len = map.get(i).length();
while (len > 0){
count++;
len /= 10;
}
i = i + count;
continue;
}
sb.append(chars[i]);
}
if (isSame(sb.toString(), s)){
System.out.println(sb.toString());
return;
}
System.out.println("!error");
}
public static boolean isSame(String str, String target){
Map<Integer, String> map = new HashMap<>();
String reg = "([a-zA-Z])\\1{2,}";
Matcher matcher = Pattern.compile(reg).matcher(str);
while (matcher.find()){
int start = matcher.start();
String group = matcher.group();
map.put(start, group);
}
char[] chars = str.toCharArray();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < chars.length; i++) {
if (map.containsKey(i)){
sb.append(map.get(i).length());
sb.append(chars[i]);
i = i + map.get(i).length() - 1;
continue;
}
sb.append(chars[i]);
}
return sb.toString().equals(target);
}
}
OD274：最长公共后缀
import java.util.Scanner;
import java.util.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String s = new StringBuilder(in.nextLine()).reverse().toString().replaceAll("\"", "");
int count = 0;
String[] split = s.substring(1, s.length() - 1).split(",");
int min = Integer.MAX_VALUE;
for (String s1 : split) {
min = Math.min(min, s1.length());
}
Set<String> set = new HashSet<>();
StringBuilder res = new StringBuilder();
for (int i = 0; i < min; i++) {
String temp = "";
for (int j = 0; j < split.length; j++) {
temp = split[j].charAt(i)+""; // 有实力就留下来
set.add(temp+"");
if (set.size() > 1){ // 只要有一个不符合，就return了
if (res.length() == 0){
System.out.println("@Zero"); // 一个都没找到，返回特殊值
}else {
System.out.println(res.reverse());
}
return;
}
}
set.clear();
res.append(temp);
}
System.out.println(res.reverse());
}
}
149. 求字符串中所有整数的最小和
注意点：
- 没有数字
- 大数
- BigInteger.add（）不会改变原数据
- 要引入 math 包
import java.util.Scanner;
import java.util.;
import java.util.regex.;;
import java.math.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String s = in.nextLine();
String reg = "-[0-9]+";
Matcher matcher = Pattern.compile(reg).matcher(s);
Map<Integer, String> map = new HashMap<>();
while (matcher.find()){
int start = matcher.start();
String str = matcher.group(0);
map.put(start, str); // 记录负数起始位置，和字符串
}
StringBuilder sb = new StringBuilder();
char[] chars = s.toCharArray();
for (int i = 0; i < chars.length; i++) {
if (map.containsKey(i)){
sb.append(map.get(i) + " ");
i = i + map.get(i).length() - 1;
continue;
}
if (Character.isDigit(chars[i])){
sb.append(chars[i] + " ");
}
}
if (sb.length() == 0){
System.out.println(0);
return;
}
BigInteger res = new BigInteger("0");
String[] split = sb.toString().split(" ");
for (String s1 : split) {
res = res.add(new BigInteger(s1));
}
System.out.println(res);
}
}
146. 敏感字段加密
import java.util.Scanner;
import java.util.*;
import java.util.regex.*;;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>(); // 记录引号相关字符位置
Scanner in = new Scanner(System.in);
int index = Integer.parseInt(in.nextLine());
String s = in.nextLine();
StringBuilder sb = new StringBuilder();
String reg = "\"\"|\"[a-zA-Z0-9_]+\""; // 注意空格不能随意些，否则会匹配上！！！
Matcher matcher = Pattern.compile(reg).matcher(s);
while (matcher.find()){
int start = matcher.start();
String s1 = matcher.group().replaceAll("_", ","); // 1. 特殊处理
map.put(start, s1);
}
String[] split = s.split("");
for (int i = 0; i < split.length; i++) {
if (map.containsKey(i)){
sb.append(map.get(i) + "_");
i = i + map.get(i).length() - 1;
continue;
}
sb.append(split[i]);
}
String temp = sb.toString().replaceAll("[_]+", "_");
if (temp.startsWith("_")){ // 处理用例：___111___，除掉首尾的 _
temp = temp.substring(1);
}
if (temp.endsWith("_")){
temp = temp.substring(0, temp.length() - 1);
}
StringBuilder res = new StringBuilder();
String[] split1 = temp.split("_");
if (index <= split1.length - 1){
split1[index] = "******";
for (String s1 : split1) {
String replace = s1.replace(",", "_"); // 2. 还原
res.append(replace + "_");
}
System.out.println(res.toString().substring(0, res.length() - 1));
return;
}
System.out.println("ERROR");
}
}
262. 计算误码率
import java.util.Scanner;
import java.util.*;
import java.util.regex.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String str1 = getStr(in.nextLine());
String str2 = getStr(in.nextLine());
int len = str1.length();
int count = 0;
for (int i = 0; i < len; i++) {
if (str1.charAt(i) != str2.charAt(i)){
count++;
}
}
System.out.println(count + "/" + len);
}
public static String getStr(String str){
String reg = "\\d+[^0-9]"; // 非数字字符
StringBuilder sb = new StringBuilder();
Matcher matcher = Pattern.compile(reg).matcher(str);
while (matcher.find()){
String group = matcher.group();
int count = Integer.parseInt(group.substring(0, group.length() - 1));
char c = group.charAt(group.length() - 1);
for (int i = 0; i < count; i++) {
sb.append(c);
}
}
return sb.toString();
}
}
273. 增强的 strstr【⭐】
将括号内的所有东西都当作普通字符：
- 如果不是转义字符 \ 的话，那么就加上 2个 \即可，但是 Java 中，2个 \ ==> \，所以要在前面加上4个\
- 是转义字符 \ 的话 ==> \ 的转义为 \\：即要在前面加上3个\，所以 3 * 2 = 6个 \
import java.util.Scanner;
import java.util.*;
import java.util.regex.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String s = in.nextLine();
String reg = in.nextLine();
StringBuilder sb = new StringBuilder();
char[] chars = reg.toCharArray();
for (int i = 0; i < chars.length; i++) {
String temp = reg.substring(i, i + 1);
if ("[".equals(temp)){
sb.append("[");
while (!"]".equals(reg.substring(i + 1, i + 2))) {
if (!"\\".equals(reg.substring(i + 1, i + 2))) { // 当前不是 \
sb.append("\\\\" + reg.substring(i + 1, i + 2));
i++;
}else {
sb.append("\\\\\\" + reg.substring(i + 1, i + 2));
i++;
}
}
sb.append("]"); // 加上最后一个 ]
i++;
}else {
sb.append(temp);
}
}
Matcher matcher = Pattern.compile(sb.toString()).matcher(s);
if (matcher.find()){
System.out.println(matcher.start());
return;
}
System.out.println("-1");
}
}
