字符串中第二大的数字【LC1796】

Given an alphanumeric string s, return the second largest numerical digit that appears in s, or -1 if it does not exist.

An alphanumeric string is a string consisting of lowercase English letters and digits.

快快学完今天的，然后去做菜

• 思路：遍历字符串，使用变量记录字符串中第一大firstHfirstHfirstH和第二大的整数值secondHsecondHsecondH，当遇到一个整数numnumnum时进行判断

  • 当num>firstHnum>firstHnum>firstH时，numnumnum即为当前数组第一大，firstHfirstHfirstH为第二大
  • 当numsecondHnum>secondHnum>secondH时，numnumnum即为当前数组第二大
  • 注意：当num==firstHnum==firstHnum==firstH时，不做任何处理

• 实现

  class Solution {public int secondHighest(String s) {int firstH = -1;int secondH = -1;for (char c : s.toCharArray()){if (c >= '0' && c <= '9'){int num = c -'0';if (num > firstH) {secondH = firstH;firstH = num;}else if (num < firstH && num > secondH) {secondH = num;}}}return secondH;}
  }
  

  • 复杂度

    • 时间复杂度：O(n)O(n)O(n)
    • 空间复杂度：O(1)O(1)O(1)