算法练习（8）：牛客在线编程08 字符串

向右看齐 2023-10-14 23:51 47阅读 0赞

package jz.bm;
    
    import java.util.Arrays;
    
    public class bm8 {
        
        /**
         * BM83 字符串变形
         */
        public String trans(String s, int n) {
        
            StringBuilder res = new StringBuilder();
            //大小写转换
            for (int i = 0; i < n; i++) {
        
                if (s.charAt(i) >= 'a' && s.charAt(i) <= 'z') {
        
                    res.append(Character.toUpperCase(s.charAt(i)));
                } else if (s.charAt(i) >= 'A' && s.charAt(i) <= 'Z') {
        
                    res.append(Character.toLowerCase(s.charAt(i)));
                } else {
        
                    res.append(s.charAt(i));
                }
            }
            //反转顺序
            res = res.reverse();
            //单词顺序转换
            for (int i = 0; i < n; i++) {
        
                if (res.charAt(i) != ' ') {
        
                    int j = i; //每个单词的起点
                    while (j < n && res.charAt(j) != ' ') {
        
                        j++;
                    }
                    StringBuilder stringBuilder = new StringBuilder(res.substring(i, j));
                    res.replace(i, j, stringBuilder.reverse().toString());
                    i = j;
                }
            }
            return res.toString();
        }
        /**
         * BM84 最长公共前缀
         */
        public String longestCommonPrefix (String[] strs) {
        
            if (strs.length == 0) {
        
                return "";
            }
            StringBuilder res = new StringBuilder();
            for (int i = 0; i < strs[0].length(); i++) {
        
                char c = strs[0].charAt(i);
                for (int j = 1; j < strs.length; j++) {
        
                    if (i >= strs[j].length() || strs[j].charAt(i) != c) {
        
                        return res.toString();
                    }
                }
                res.append(c);
            }
            return res.toString();
        }
        /**
         * BM85 验证IP地址
         */
        public String solve (String IP) {
        
            if (ipv4(IP)) {
        
                return "IPv4";
            } else if (ipv6(IP)) {
        
                return "IPv6";
            } else {
        
                return "Neither";
            }
        }
    
        private boolean ipv4(String IP) {
        
            String[] strings = IP.split("\\.");
            //防止尾部是.
            if (strings.length != 4 || IP.endsWith(".")) {
        
                return false;
            }
            for (int i = 0; i < 4; i++) {
        
                if (strings[i].length() == 0) {
        
                    return false;
                }
                for (int j = 0; j < strings[i].length(); j++) {
        
                    //开头不能为0
                    if (j == 0 && strings[i].charAt(j) == '0') {
        
                        return false;
                    }
                    //10进制
                    if (strings[i].charAt(j) > '9' || strings[i].charAt(j) < '0') {
        
                        return false;
                    }
                }
                //0-255
                int num = Integer.parseInt(strings[i]);
                if (num < 0 || num > 255) {
        
                    return false;
                }
            }
            return true;
        }
    
        private boolean ipv6(String IP) {
        
            String[] strings = IP.split("\\:");
            //防止尾部是:
            if (strings.length != 8 || IP.endsWith(":")) {
        
                return false;
            }
            for (int i = 0; i < 8; i++) {
        
                //不为null,没有多余的0
                if (strings[i].length() == 0 || strings[i].length() > 4 || strings[i].startsWith("00")) {
        
                    return false;
                }
                for (int j = 0; j < strings[i].length(); j++) {
        
                    //16进制
                    if (!((strings[i].charAt(j) >= '0' && strings[i].charAt(j) <= '9')
                    || (strings[i].charAt(j) >= 'a' && strings[i].charAt(j) <= 'f')
                    || (strings[i].charAt(j) >= 'A' && strings[i].charAt(j) <= 'F'))) {
        
                        return false;
                    }
                }
            }
            return true;
        }
    
        /**
         * BM86 大数加法
         */
        public String solve (String s, String t) {
        
            if (s == null || s.equals("")) {
        
                return t;
            }
            if (t == null || t.equals("")) {
        
                return s;
            }
            int i = s.length() - 1, j = t.length() - 1;
            int carry = 0;
            StringBuilder res = new StringBuilder();
            while (i >= 0 || j >= 0) {
        
                int a = i < 0 ? 0 : s.charAt(i) - '0';
                int b = j < 0 ? 0 : t.charAt(j) - '0';
                res.append((a + b + carry) % 10);
                carry = (a + b + carry) / 10;
                i--;
                j--;
            }
            if (carry != 0) {
        
                res.append(carry);
            }
            return res.reverse().toString();
        }
    }