leetcode解题

125.valid-palindrome.java

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+/*
+ * @lc app=leetcode id=125 lang=java
+ *
+ * [125] Valid Palindrome
+ */
+
+// @lc code=start
+class Solution {
+    public boolean isPalindrome(String s) {
+        int i = 0, j = s.length()-1;
+        boolean r = true;
+        while(i < j) {
+            while(i<j && !isAlphanumberic(s.charAt(i))) {
+                i++;
+            }
+            while(i<j && !isAlphanumberic(s.charAt(j))) {
+                j--;
+            }
+            if(i==j) {
+                break;
+            }
+            if(!isSameLeterIgnoreCase(s.charAt(i), s.charAt(j))) {
+                r = false;
+                break;
+            }
+        }
+        return r;
+    }
+
+    private boolean isAlphanumberic(char c) {
+        return c >= 'a' && c <= 'z' || 
+        c >= 'A' && c <= 'Z' || c >='0' && c <= '9';
+    }
+
+    private boolean isSameLeterIgnoreCase(char a, char b) {
+        return a == b || a - b == 'z' - 'a' || a - b == 'a' - 'z';
+    }
+}
+// @lc code=end
+