Solution#1
public class Solution {
public String addStrings(String num1, String num2) {
if (num1.equals("0"))
return num2;
if (num2.equals("0"))
return num1;
int length1 = num1.length();
int length2 = num2.length();
String result = "";
int carry = 0;
int i = length1 - 1;
int j = length2 - 1;
int tmp;
while (i >= 0 && j >= 0) {
tmp = (num1.charAt(i--) - '0') + (num2.charAt(j--) - '0') + carry;
carry = tmp / 10;
result = tmp % 10 + result;
}
while (i >= 0) {
tmp = num1.charAt(i--) - '0' + carry;
carry = tmp / 10;
result = tmp % 10 + result;
}
while (j >= 0) {
tmp = num2.charAt(j--) - '0' + carry;
carry = tmp / 10;
result = tmp % 10 + result;
}
return carry == 0 ? result : "1" + result;
}
}
Problem#1
- 效率太低了,12%
- 改成StringBuilder快很多