165. Compare Version Numbers
class Solution { public int compareVersion(String version1, String version2) { String[] levels1 = version1.split("\."); String[] levels2 = version2.split("\."); int length = Math.max(levels1.length, levels2.length); for(int i = 0; i < length; i++){ Integer v1 = i < levels1.length ? Integer.parseInt(levels1[i]) : 0; Integer v2 = i < levels2.length ? Integer.parseInt(levels2[i]) : 0; int compare = v1.compareTo(v2); if(compare != 0){ return compare; } } return 0; } }
8. String to Integer (atoi)
sign: 正负号
index: 当前索引。
class Solution { public int myAtoi(String str) { str = str.trim(); if(str == null || str.length() == 0) return 0; int sign = 1; int index = 0; char c = str.charAt(0); if(c == '+'){ sign = 1; index++; }else if(c == '-'){ sign = -1; index++; } long sum = 0; for(int i = index; i < str.length(); i++){ if(!Character.isDigit(str.charAt(i))){ return (int)sum * sign; } sum = sum * 10 + str.charAt(i) - '0'; if(sign == 1 && sum > Integer.MAX_VALUE){ return Integer.MAX_VALUE; } if(sign == -1 && (-1)*sum < Integer.MIN_VALUE){ return Integer.MIN_VALUE; } } return (int)sum * sign; } }