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53 lines
1.1 KiB
53 lines
1.1 KiB
2 years ago
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package class31;
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public class Problem_0125_ValidPalindrome {
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// 忽略空格、忽略大小写 -> 是不是回文
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// 数字不在忽略大小写的范围内
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public static boolean isPalindrome(String s) {
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if (s == null || s.length() == 0) {
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return true;
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}
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char[] str = s.toCharArray();
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int L = 0;
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int R = str.length - 1;
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while (L < R) {
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// 英文（大小写） + 数字
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if (validChar(str[L]) && validChar(str[R])) {
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if (!equal(str[L], str[R])) {
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return false;
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}
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L++;
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R--;
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} else {
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L += validChar(str[L]) ? 0 : 1;
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R -= validChar(str[R]) ? 0 : 1;
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}
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}
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return true;
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}
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public static boolean validChar(char c) {
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return isLetter(c) || isNumber(c);
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}
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public static boolean equal(char c1, char c2) {
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if (isNumber(c1) || isNumber(c2)) {
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return c1 == c2;
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}
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// a A 32
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// b B 32
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// c C 32
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return (c1 == c2) || (Math.max(c1, c2) - Math.min(c1, c2) == 32);
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}
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public static boolean isLetter(char c) {
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return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
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}
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public static boolean isNumber(char c) {
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return (c >= '0' && c <= '9');
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}
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}
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