[英]Segmentation fault adding two large numbers represented as strings
Here is the code snippet or rather a function which takes two strings as inputs which are basically large integers and prints the sum of them. 这是代码段,或者说是一个函数,该函数将两个字符串作为输入,它们基本上是大整数,并打印它们的总和。 I am getting the sum printed correctly, but a segmentation fault comes up at the end and I am unable to figure out its source. 我可以正确打印总和,但是最后出现分割错误,我无法弄清其来源。
string sum(string x, string y) {
bool carry = false;
int yLen = y.length(), xLen = x.length();
vector<char> s;
for(int i = xLen - 1, j = yLen - 1; i >= 0, j >= 0; i--, j--) {
int a = x[i] - '0', b = y[j] - '0';
int c = (carry?(a+b+1):(a+b));
if(c/10) carry = true, c %= 10;
else carry = false;
s.push_back(c + '0');
}
for(int i = xLen - yLen - 1; i >= 0; i--) {
int a = x[i] - '0';
int c = (carry?(a+1):(a));
if(c/10) carry = true, c %= 10;
else carry = false;
s.push_back(c + '0');
}
reverse(s.begin(), s.end());
for(vector<char>::iterator i = s.begin(); i != s.end(); i++) cout<<*i;
cout<<endl;
}
Update: Assume that x.length() is always greater than or equal to y.length() in the input itself. 更新:假设x.length()在输入本身中始终大于或等于y.length()。
Your function returns string
. 您的函数返回string
。
You need to return a string, or change that to void
. 您需要返回一个字符串,或将其更改为void
。
void sum(string x, string y) {
Not returning in a value-returning function is undefined behaviour and is probably the cause of your segmentation fault. 不返回值返回函数是未定义的行为 ,可能是分段错误的原因。
This loop statement 此循环语句
for(int i = xLen - 1, j = yLen - 1; i >= 0, j >= 0; i--, j--) {
is already wrong. 已经错了。
The second expression in the loop 循环中的第二个表达式
i >= 0, j >= 0
is an expression of the comma operator. 是逗号运算符的表达式。 It does not take into account that i can be less than 0. The value of the expression is the value of the condition j >= 0. So if xLen is less than yLen then you will get that i will be equal to some negative number. 它不考虑i可以小于0。表达式的值是条件j> = 0的值。因此,如果xLen小于yLen,则将得到i等于某个负数。
You should rewrite this loop. 您应该重写此循环。 I think you meant expresssion 我想你的意思是表达
i >= 0 && j >= 0
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