package leetcode.string; /* * @description: 8.字符串转换整数 (atoi) * @param: 字符串,允许开头为空格,可能包含其他字符 * @return: 字符串转换后的整数,如果超过32有符号整数的最值,就返回最值 * @author: cp * @date: 2020/8/3 */ public class MyAtoi { public int myAtoi(String str) { int start = 0; int result = 0; int tmpResult = 0; int invalidResult = 0; int positive = 1; int l = str.length(); //首先去除空格 for (; start < l; start++) { if (str.charAt(start) != ' ') break; } if (start == l) { return invalidResult; } //判断首位是不是符号 int firstChar = str.charAt(start); if (firstChar == '+') { start++; positive = 1; } else if (firstChar == '-') { start++; positive = -1; } else if (firstChar < '0' || firstChar > '9') { return invalidResult; } for (; start < l; start++) { char c = str.charAt(start); //有效字符串 if (c >= '0' && c <= '9') { tmpResult = tmpResult * 10 + (c - 48);//ascii码 //溢出情况 if (result != 0 && tmpResult / result < 10) { if (positive == 1) { return Integer.MAX_VALUE; } else { return Integer.MIN_VALUE; } } result = tmpResult; } else { //无效字符串 break; } } return positive * result; } }