{"id":2002,"date":"2016-04-22T12:40:27","date_gmt":"2016-04-22T04:40:27","guid":{"rendered":"http:\/\/boweihe.me\/?p=2002"},"modified":"2016-04-22T12:40:27","modified_gmt":"2016-04-22T04:40:27","slug":"leetcode-9-palindrome-number","status":"publish","type":"post","link":"https:\/\/dayandcarrot.space\/?p=2002","title":{"rendered":"LeetCode 9. Palindrome Number"},"content":{"rendered":"

\u9898\u76ee<\/h3>\n

Determine whether an integer is a palindrome. Do this without extra space.<\/p>\n

Some hints:<\/b>Could negative integers be palindromes? (ie, -1)
\nIf you are thinking of converting the integer to string, note the restriction of using extra space.
\nYou could also try reversing an integer. However, if you have solved the problem “Reverse Integer”, you know that the reversed integer might overflow. How would you handle such case?
\nThere is a more generic way of solving this problem.<\/p>\n

\u601d\u8def<\/h3>\n

\u9996\u5148\u8981\u6ce8\u610f\uff0c\u8d1f\u6570\u4e0d\u662f\u56de\u6587\u6570\u3002
\n\u7136\u540e\u9898\u76ee\u4e2d\u8981\u6c42\u4e0d\u80fd\u4f7f\u7528\u989d\u5916\u7684\u7a7a\u95f4\uff0c\u6211\u7684\u7406\u89e3\u662fO(1)\u7a7a\u95f4\u590d\u6742\u5ea6\uff0c\u5373\u4e0d\u80fd\u7528\u5b57\u7b26\u4e32\u6765\u5b58\u50a8?<\/p>\n

\u4ee3\u7801<\/h3>\n

\u6211\u8fd9\u4e2a\u89e3\u51b3\u65b9\u6848\u4e0d\u77e5\u9053\u662f\u4e0d\u662f\u8fdd\u89c4\u4e86\uff0c\u5982\u679c\u518d\u82db\u523b\u4e00\u70b9\uff0c\u90a3\u5c31\u662f\u6bcf\u6b21\u6d4b\u8bd5\u5f53\u524d\u6570\u5b57\u7684\u4f4d\u6570\uff08\u8fde\u7eed\u966410\uff09\uff0c\u7136\u540e\u7528\u9664\u6cd5\u548c\u6a2110\u5224\u65ad\u9996\u4f4d\u548c\u672b\u5c3e\u7684\u6570\u5b57\u3002<\/p>\n

class Solution {\npublic:\n    bool isPalindrome(int x) {\n        if(x < 0)\n            return false;\n        int cover = 1;\n        int x_copy = x;\n        while(x_copy\/10 > 0){\n            x_copy \/= 10;\n            cover *= 10;\n        }\n        while(cover >= 10){\n            int front = x\/cover;\n            int end = x%10;\n            if(front != end){\n                return false;\n            }\n            x -= front * cover;\n            x \/= 10;\n            cover \/= 100;\n        }\n        return true;\n    }\n};<\/pre>\n
 \n<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"
\u9898\u76ee Determine whether an integer is a palindrome. Do this without extra space. Some hints:Could negative integers be palindromes? (ie, -1) If you are thinking of converting the integer to string, note the restriction of using extra space. You could also try reversing an integer. However, if you have solved the problem “Reverse Integer”, you […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[66],"class_list":["post-2002","post","type-post","status-publish","format-standard","hentry","category-study","tag-leetcode-oj"],"_links":{"self":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts\/2002","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2002"}],"version-history":[{"count":0,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=\/wp\/v2\/posts\/2002\/revisions"}],"wp:attachment":[{"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2002"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2002"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dayandcarrot.space\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2002"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}