Making up a string from second string, order of characters - c++

Question

Basically I need to check if the characters found in second string can make the first string. The program works, however I have this problem that it doesn't take the character order in mind.
For example if I input:
UMC UniverseCeeMake ==> Yes
but it should input No because UMC != UCM, how can I make it check the character order aswell? can someone assist?
#include <iostream>
#include <string>
using namespace std;
const int MAX = 256;
bool canMakeStr2(string str1, string str2)
{
int count[MAX] = {0};
for (int i = 0; i < str1.length(); i++)
count[str1[i]]++;
for (int i = 0; i < str2.length(); i++)
{
if (count[str2[i]] == 0)
return false;
count[str2[i]]--;
}
return true;
}
int main()
{
int n;
string str1;
string str2;
cin>>n;
for(int i =0;i<n;i++){
cin >> str1 >> str2;
if(str1.length()<=10000 && str2.length()<=10000)
if (canMakeStr2(str2, str1))
cout << "Yes";
else
cout << "No";
}
return 0;
}

Answer 1

As Fabian has alread stated. You approach with counting letters will not work. You will never cover the sequence.
You need to select a different approach. The most easy one is to use the std::strings existing find function.
So, you will go over all characters in the given character set in the correct sequence with a simple range based for loop. Then you can use the find function to check, if the character is existing in the other string.
To ensure the sequence, you must not search always from the beginning, but from the last poasition (+1) where a character was found. This will keep the ensure the sequence.
Example:
UMC UniverseCeeMake
Search for the 'U' starting from the beginning
'U' Found at position 0. Increment start position to 1
Search for 'M' staring from position 1
'M' found at position 11 (already behind the 'C'). Increment start position to 12
Search for a 'C' starting at position 12
Cannot be found --> Result will be "No"
This can be implemented very easyly:
#include <iostream>
#include <string>
bool canMakeStr(std::string toBeChecked, std::string characterSet) {
// Result of function. We assume that it will work
bool result{ true };
// position, where we find a charcted in the string to be checked
size_t position{};
// Go through all characters from the given character set
for (const char c : characterSet) {
// Look, where this character has been found
position = toBeChecked.find(c, position);
// If we could not find the character in the string to be checked
if (position == std::string::npos) {
// Then the result is false
result = false;
break;
}
else {
// Character was found. Now, we implement the solution to check for the sequence
// We will not start to search again at the beginning, but after the just found character
// This will ensure that we keep the sequence
++position;
}
}
return result;
}
int main()
{
// Read the number of test cases
unsigned int numberOfTestCases; std::cin >> numberOfTestCases;
// Work on all test cases
while (numberOfTestCases--) {
// Read the 2 strings
std::string characterSet, toBeChecked; std::cin >> characterSet >> toBeChecked;
// And check for the result
if (canMakeStr(toBeChecked, characterSet))
std::cout << "Yes\n";
else
std::cout << "No\n";
}
return 0;
}