JZ-049 - Convert String to Integer

convert string to integer

Topic description

Converting a string to an integer requires library functions that cannot use strings to convert integers. Returns 0 if the value is 0 or the string is not a valid value

• Enter description:
• Enter a string, including alphanumeric characters, can be empty
• Return value description:
• Returns the number if it is a valid numeric representation, otherwise returns 0

title link : converts a string to an integer

code

/**
 * 标题：把字符串转换成整数
 * 题目描述
 * 将一个字符串转换成一个整数，要求不能使用字符串转换整数的库函数。 数值为0或者字符串不是一个合法的数值则返回0
 * 输入描述:
 * 输入一个字符串,包括数字字母符号,可以为空
 * 返回值描述:
 * 如果是合法的数值表达则返回该数字，否则返回0
 * 题目链接：
 * https://www.nowcoder.com/practice/1277c681251b4372bdef344468e4f26e?tpId=13&&tqId=11202&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
 */
public class Jz49 {

    public int strToInt(String str) {
        if (str == null || str.length() == 0) {
            return 0;
        }
        boolean isNegative = str.charAt(0) == '-';
        int result = 0;
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (i == 0 && (c == '+' || c == '-')) {
                continue;
            }
            if (c < '0' || c > '9') {
                return 0;
            }
            result = result * 10 + (c - '0');
        }
        return isNegative ? -result : result;
    }

    public static void main(String[] args) {
        Jz49 jz49 = new Jz49();
        System.out.println(jz49.strToInt("[phone]a"));
        System.out.println(jz49.strToInt("+2392032"));
        System.out.println(jz49.strToInt("2293043a"));
        System.out.println(jz49.strToInt("-fd3323"));
        System.out.println(jz49.strToInt("-23232942"));
        System.out.println(jz49.strToInt("292930203"));
    }
}

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