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LeetCode415 - Add Strings 用字符串模拟整数相加

2017-04-09 21:51 169 查看

原文链接：http://www.cnblogs.com/vincent93/p/6686627.html

415. Add Strings

Given two non-negative integers

num1

and

num2

represented as string, return the sum of

num1

and

num2

Note:

The length of both
```
num1
```
and
```
num2
```
is < 5100.
Both
```
num1
```
and
```
num2
```
contains only digits
```
0-9
```
.
Both
```
num1
```
and
```
num2
```
does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.

思路：控制num1的长度不小于num2的长度，在num1上直接做修改。

class Solution {
public:
string addStrings(string num1, string num2)
{
int len1 = num1.size(), len2 = num2.size();
if (len2 > len1)
{
swap(len1, len2);
swap(num1, num2);
}
int i = len1 - 1, j = len2 - 1;
int carry = 0, a = 0, b = 0, sum = 0;
while (i >= 0)
{
a = num1[i] - '0';
if (j >= 0)
b = num2[j] - '0';
else
b = 0;
sum = a + b + carry;
if (sum >= 10)
{
sum -= 10;
carry = 1;
}
else
carry = 0;
num1[i] = sum + '0';
--i;--j;
}
if (carry == 1)
num1 = '1' + num1;
return num1;
}
};

转载于:https://www.cnblogs.com/vincent93/p/6686627.html

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