Wrong answer in c++ - c++

Question

You are given a DNA sequence, and few enzymes. Suppose, a DNA sequence goes like this : ATGCTGCTATGCATGCAGTGACT, and you are given enzymes which can remove AT and GC sequences. Thereby, you need to remove all occurrences of AT from the DNA first and then reform the DNA and apply the next enzyme to remove all occurrences of GC. The output of the problem would be the string you get at last reforming the pieces which are not removed by these enzymes.
Input
The first line of input consists of an integer n that denotes the number of enzymes. The first line has the DNA sequence. The next T lines has the input B1, B2, B3... Bn.
Output
For given input DNA sequence, output a single line containing the final reformed DNA that is formed by repeatedly removing all the occurrences of B1, B2, B3... Bn from A.
In case the DNA is completely consumed print 0 to indicate that there is no DNA left.
Constraints
1 <= n <= 10
Example 1:
Input:
2
ATACGCATGACGATGCATGCAGCAT
ATA
GC
Output:
CATGACGATATAAT
Example 2:
Input:
3
ATGCATGCATCGACTCAGCATCAGCATCGACTA
TG
GC
AT
Output:
ACACCGACTCACACGACTA
My code:
I tried solving it using string in c++, I am getting :
terminate called after throwing an instance of 'std::out_of_range'
what():basic_string::erase()
#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <math.h>
#include <vector>
#include <set>
#include <stdlib.h>
#include <string.h>
#include <queue>
#include <stack>
#include <assert.h>
#include <limits.h>
using namespace std;
int main() {
string str, str1;
int n;
scanf("%d", &n);
cin >> str;
while (n--) {
cin >> str1;
int len = str1.length();int len1=str.length();
for (int i = 0; i < len1; i++) {
int found = str.find(str1);
str.erase(found, found + len);
}
}
cout << str;
return 0;
}

Answer 1

Three main problems:
Number one, out of range exception on string::erase.
Fixed by testing that find actually returned a value:
if (found!=std::string::npos)
Number two, searching correctly.
Fixed by keeping track of found (it's also a size_t not an int) and searching from the next location:
found = str.find(str1,found);
Number three, using string::erase properly.
Fixed by using length of substring to erase, not length + position:
str.erase(found,len);
I still haven't added any input validation to your code. You should really think about doing that yourself.
Final code:
(ideone)
#include <string>
#include <iostream>
int main()
{
std::string str;
std::string str1;
int n;
std::cin>>n;
std::cin>>str;
while(n--)
{
std::cin>>str1;
int len = str1.length();
size_t found = 0;
for(unsigned int i=0;i<str.length();i++)
{
found = str.find(str1,found);
if (found!=std::string::npos)
{
str.erase(found,len);
}
else
{
break;
}
}
}
std::cout<<(str.length()?str:"0");
return 0;
}
idone output for each example input (I've added your example outputs in between the /* */ marks):
Success time: 0 memory: 3476 signal:0
CATGACGATATAAT
/*CATGACGATATAAT*/
Success time: 0 memory: 3476 signal:0
ACACCGACTCACACGACTA
/*ACACCGACTCACACGACTA*/