2019-11-02 12:07:41 +08:00
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# 67. 把字符串转换成整数
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2019-11-03 23:57:08 +08:00
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## 题目链接
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2019-11-02 12:07:41 +08:00
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[NowCoder](https://www.nowcoder.com/practice/1277c681251b4372bdef344468e4f26e?tpId=13&tqId=11202&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
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## 题目描述
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将一个字符串转换成一个整数，字符串不是一个合法的数值则返回 0，要求不能使用字符串转换整数的库函数。
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```html
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Iuput:
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+2147483647
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1a33
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Output:
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2147483647
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0
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```
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## 解题思路
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```java
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public int StrToInt(String str) {
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2020-05-27 00:44:06 +08:00
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if (str == null || str.length() == 0)
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return 0;
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boolean isNegative = str.charAt(0) == '-';
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int ret = 0;
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for (int i = 0; i < str.length(); i++) {
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char c = str.charAt(i);
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if (i == 0 && (c == '+' || c == '-')) /* 符号判定 */
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continue;
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if (c < '0' || c > '9') /* 非法输入 */
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2019-11-02 12:07:41 +08:00
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return 0;
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2020-05-27 00:44:06 +08:00
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ret = ret * 10 + (c - '0');
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2019-11-02 12:07:41 +08:00
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}
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2020-05-27 00:44:06 +08:00
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return isNegative ? -ret : ret;
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}
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2019-11-02 12:07:41 +08:00
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```
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2019-11-02 17:33:10 +08:00
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<div align="center"><img width="320px" src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/githubio/公众号二维码-2.png"></img></div>
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