2243. 计算字符串的数字和

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Java：以 k 为步长进行跳！然后再延伸k

class Solution {public String digitSum(String s, int k) {while (s.length() > k) {int n = s.length();StringBuilder sb = new StringBuilder();  // sb存！for (int i = 0; i < n; i += k) {int sum = 0;for (int j = 0; j < k && i + j < n; j++) {sum += s.charAt(i + j) - '0';  // s用于遍历！}sb.append(sum);}s = sb.toString();}return s;}
}

Java：自己搓的代码…

class Solution {public String digitSum(String s, int k) {StringBuilder str = new StringBuilder(s);int len = s.length();while (len > k) {String s1 = new String(str);str.delete(0, str.length());int a = 0;for (int i = 0; i < len; ++i) {// a += Integer.valueOf(s1.charAt(i));  // error 入参是Stringa += s1.charAt(i) - '0';if((i+1) % k == 0) {str.append(String.valueOf(a));a = 0;}}if (len % k != 0) {int b = 0;for (int i = len - len % k; i < len; i++) {b += s1.charAt(i) - '0';}str.append(String.valueOf(b));}len = str.length();}return String.valueOf(str);}
}