Maximize a Number by Rounding Digits - C++ Solution

Here is a possible C++ solution for the problem:
\n```cpp
#include
#include
#include
using namespace std;

int main() {
int t;
cin >> t;

while(t--) {
string x;
cin >> x;

int n = x.length();
int k = 0;
for(int i = n-1; i >= 0; i--) {
if(x[i] >= '5') {
k = i;
break;
}
}

for(int i = k; i < n; i++) {
if(x[i] == '9') {
x[i] = '0';
if(i == n-1) {
x = '1' + x;
n++;
}
} else {
x[i]++;
}
}

for(int i = 0; i < k; i++) {
x[i] = '0';
}

cout << x << endl;
}

return 0;
}\

\
This solution iterates through each test case, and for each test case, it finds the rightmost position `k` where the digit is greater than or equal to 5. Then, it increases the digit at position `k` by 1 and replaces all digits before position `k` with zeros. If the digit at position `k` is 9, it replaces it with 0 and searches for the next position `k'` where the digit is less than 9 to increase it by 1. Finally, it outputs the resulting number.