{
   "question_id": 65,
   "question_title": "有效数字",
   "difficulty": "困难",
   "question_content": "<p><strong>有效数字</strong>（按顺序）可以分成以下几个部分：</p><ol>\t<li>一个 <strong>小数</strong> 或者 <strong>整数</strong></li>\t<li>（可选）一个 <code>'e'</code> 或 <code>'E'</code> ，后面跟着一个 <strong>整数</strong></li></ol><p><strong>小数</strong>（按顺序）可以分成以下几个部分：</p><ol>\t<li>（可选）一个符号字符（<code>'+'</code> 或 <code>'-'</code>）</li>\t<li>下述格式之一：\t<ol>\t\t<li>至少一位数字，后面跟着一个点 <code>'.'</code></li>\t\t<li>至少一位数字，后面跟着一个点 <code>'.'</code> ，后面再跟着至少一位数字</li>\t\t<li>一个点 <code>'.'</code> ，后面跟着至少一位数字</li>\t</ol>\t</li></ol><p><strong>整数</strong>（按顺序）可以分成以下几个部分：</p><ol>\t<li>（可选）一个符号字符（<code>'+'</code> 或 <code>'-'</code>）</li>\t<li>至少一位数字</li></ol><p>部分有效数字列举如下：</p><ul>\t<li><code>[\"2\", \"0089\", \"-0.1\", \"+3.14\", \"4.\", \"-.9\", \"2e10\", \"-90E3\", \"3e+7\", \"+6e-1\", \"53.5e93\", \"-123.456e789\"]</code></li></ul><p>部分无效数字列举如下：</p><ul>\t<li><code>[\"abc\", \"1a\", \"1e\", \"e3\", \"99e2.5\", \"--6\", \"-+3\", \"95a54e53\"]</code></li></ul><p>给你一个字符串 <code>s</code> ，如果 <code>s</code> 是一个 <strong>有效数字</strong> ，请返回 <code>true</code> 。</p><p> </p><p><strong>示例 1：</strong></p><pre><strong>输入：</strong>s = \"0\"<strong><br />输出：</strong>true</pre><p><strong>示例 2：</strong></p><pre><strong>输入：</strong>s = \"e\"<strong><br />输出：</strong>false</pre><p><strong>示例 3：</strong></p><pre><strong>输入：</strong>s = \".\"<strong><br />输出：</strong>false</pre><p><strong>示例 4：</strong></p><pre><strong>输入：</strong>s = \".1\"<strong><br />输出：</strong>true</pre><p> </p><p><strong>提示：</strong></p><ul>\t<li><code>1 <= s.length <= 20</code></li>\t<li><code>s</code> 仅含英文字母（大写和小写），数字（<code>0-9</code>），加号 <code>'+'</code> ，减号 <code>'-'</code> ，或者点 <code>'.'</code> 。</li></ul>",
   "topic_link": "https://bbs.csdn.net/topics/600470924",
   "cpp": "#include <stdio.h>\n#include <stdlib.h>\n#include <stdbool.h>\n#include <ctype.h>\nstatic bool isNumber(const char *s)\n{\n\twhile (*s == ' ')\n\t\t++s;\n\tbool if_find_num = false;\n\tif (*s == '-' || *s == '+')\n\t\t++s;\n\twhile (isdigit(*s))\n\t{\n\t\tif_find_num = true;\n\t\t++s;\n\t}\n\tif (*s == '.')\n\t\t++s;\n\twhile (isdigit(*s))\n\t{\n\t\tif_find_num = true;\n\t\t++s;\n\t}\n\tif (if_find_num == true && *s == 'e')\n\t{\n\t\t++s;\n\t\tif (*s == '+' || *s == '-')\n\t\t\t++s;\n\t\tif_find_num = false;\n\t\twhile (isdigit(*s))\n\t\t{\n\t\t\tif_find_num = true;\n\t\t\t++s;\n\t\t}\n\t}\n\twhile (*s == ' ')\n\t\t++s;\n\treturn *s == '\\0' && if_find_num == true;\n}\nint main(int argc, char **argv)\n{\n\tif (argc != 2)\n\t{\n\t\tfprintf(stderr, \"Usage: ./test number\\n\");\n\t\texit(-1);\n\t}\n\tprintf(\"%s\\n\", isNumber(argv[1]) ? \"true\" : \"false\");\n\treturn 0;\n}",
   "java": "class Solution {\n\tchar[] chars;\n\tboolean point = false;\n\tboolean exponent = false;\n\tpublic boolean isNumber(String s) {\n\t\ts = s.trim();\n\t\tint length = s.length();\n\t\tif (length == 0) {\n\t\t\treturn false;\n\t\t}\n\t\tchars = s.toCharArray();\n\t\tString[] ss = s.split(\"e\");\n\t\tif (ss.length == 0) {\n\t\t\treturn false;\n\t\t}\n\t\tif (ss[0].length() == 0)\n\t\t\treturn false;\n\t\tif (ss[0].length() < length)\n\t\t\texponent = true;\n\t\tif (ss[0].length() == length - 1) {\n\t\t\treturn false;\n\t\t}\n\t\tString[] pre = ss[0].split(\"\\\\.\");\n\t\tif (pre.length == 0) {\n\t\t\treturn false;\n\t\t}\n\t\tif (pre[0].length() < ss[0].length())\n\t\t\tpoint = true;\n\t\tboolean result = pre(0, pre[0].length());\n\t\tresult = result && middle(pre[0].length() + 1, ss[0].length());\n\t\tif (exponent) {\n\t\t\tresult = result && is(ss[0].length() + 1, length);\n\t\t}\n\t\treturn result;\n\t}\n\tpublic boolean pre(int i, int length) {\n\t\tif (i >= length) {\n\t\t\treturn true;\n\t\t}\n\t\tif (chars[i] == '+' || chars[i] == '-') {\n\t\t\ti++;\n\t\t}\n\t\tif (i == length && !point) {\n\t\t\treturn false;\n\t\t}\n\t\tfor (; i < length; i++) {\n\t\t\tif (chars[i] < '0' || chars[i] > '9') {\n\t\t\t\treturn false;\n\t\t\t}\n\t\t}\n\t\treturn true;\n\t}\n\tpublic boolean middle(int i, int length) {\n\t\tif (i >= length && point) {\n\t\t\tif (chars[i - 2] >= '0' && chars[i - 2] <= '9') {\n\t\t\t\treturn true;\n\t\t\t}\n\t\t\treturn false;\n\t\t}\n\t\tfor (; i < length; i++) {\n\t\t\tif (chars[i] < '0' || chars[i] > '9') {\n\t\t\t\treturn false;\n\t\t\t}\n\t\t}\n\t\treturn true;\n\t}\n\tpublic boolean is(int i, int length) {\n\t\tif (i == 1) {\n\t\t\treturn false;\n\t\t}\n\t\tif (chars[i] == '+' || chars[i] == '-') {\n\t\t\ti++;\n\t\t}\n\t\tif (i == length) {\n\t\t\treturn false;\n\t\t}\n\t\tfor (; i < length; i++) {\n\t\t\tif (chars[i] < '0' || chars[i] > '9') {\n\t\t\t\treturn false;\n\t\t\t}\n\t\t}\n\t\treturn true;\n\t}\n}",
   "js": "",
   "python": "class Solution(object):\n\tdef isNumber(self, s):\n\t\ts = s.strip()\n\t\tls, pos = len(s), 0\n\t\tif ls == 0:\n\t\t\treturn False\n\t\tif s[pos] == '+' or s[pos] == '-':\n\t\t\tpos += 1\n\t\tisNumeric = False\n\t\twhile pos < ls and s[pos].isdigit():\n\t\t\tpos += 1\n\t\t\tisNumeric = True\n\t\tif pos < ls and s[pos] == '.':\n\t\t\tpos += 1\n\t\t\twhile pos < ls and s[pos].isdigit():\n\t\t\t\tpos += 1\n\t\t\t\tisNumeric = True\n\t\telif pos < ls and s[pos] == 'e' and isNumeric:\n\t\t\tisNumeric = False\n\t\t\tpos += 1\n\t\t\tif pos < ls and (s[pos] == '+' or s[pos] == '-'):\n\t\t\t\tpos += 1\n\t\t\twhile pos < ls and s[pos].isdigit():\n\t\t\t\tpos += 1\n\t\t\t\tisNumeric = True\n\t\tif pos == ls and isNumeric:\n\t\t\treturn True\n\t\treturn False\n# %%\ns = Solution()\nprint(s.isNumber(s = \"0\"))",
   "status": 1,
   "keywords": "字符串",
   "license": {
      "cpp": "https://github.com/begeekmyfriend/leetcode",
      "python": "https://github.com/qiyuangong/leetcode",
      "java": "https://blog.csdn.net/a1439775520/article/details/104340910"
   },
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      "python": "https://codechina.csdn.net/csdn/csdn-daily-code/-/jupyter/master/data/notebook/leetcode/ipynb/64/64_python.ipynb?type=file",
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