C++ mistake in finding a 'x' number in 2D array [closed] - c++

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In my code below, I try to find an 'x' in a 2D array and display its row and column. But it always shows the a[0][1] in the result. Can someone tell me where did I wrong and why is that? I tried other code but there is no difference. Thanks
My code:
#include <iostream>
using namespace std;
int main(){
int m, n, i, j, a[m][n], sum, x, sl=0;
cout<<"insert array number of rows: "; cin>>m;
cout<<"insert array number of columns: "; cin>>n;
for(i=0;i<m;i++){
sum=0;
for(j=0;j<n;j++){
cout<<"insert board["<<i<<"]["<<j<<"]: ";
cin>>a[i][j];
sum+=a[i][j];
}
cout<<"the summary of rows "<<i<<" is: "<<sum<<endl;
}
cout<<"search x= "; cin>>x;
for (i=0; i<=m-1; i++){
for (j=0; j<=n-1; j++){
if (a[i][j]==x){
sl++;
cout<<"x is at "<<"a["<<i<<"]["<<j<<"]"<< endl;
}
}
}
if(sl==0){
cout<<"there is no x in the array";
}
cout<<sl;
return 0;
}
My results:

Answer 1

Sources of error in your code:
You were using a variable length array (which is not a part of C++ standard). Moreover you were setting its rows and columns before even initializing/inputting n and m.
Fixed Code:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int m, n, x, sl = 0;
cout << "Insert number of rows in the array: ";
cin >> m;
cout << "\nInsert number of columns in the array: ";
cin >> n;
// put the below line after cin >> m; cin >> n;
vector<vector<int>> a(m, vector<int>(n, 0)); // <-- Use this instead of int a[m][n];
cout << endl;
for (int i = 0; i < m; ++i) {
int sum = 0;
for (int j = 0; j < n; ++j) {
cout << "\nInsert board[" << i << "][" << j << "]: ";
cin >> a[i][j];
sum += a[i][j];
}
cout << "\nThe sum of the row " << i << " is: " << sum << endl;
}
cout << "\nSearch x = ";
cin >> x;
cout << '\n' << endl;
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
if (a[i][j] == x) {
sl++;
cout << "x is at a[" << i << "][" << j << "]\n";
}
}
}
if (sl == 0) { cout << "\nThere is no x in the array!"; }
else cout << '\n' << sl;
return 0;
}
Sample Input :
2
2
3
4
7
3
3
Sample Output :
Insert number of rows in the array:
Insert number of columns in the array:
Insert board[0][0]:
Insert board[0][1]:
The sum of the row 0 is: 7
Insert board[1][0]:
Insert board[1][1]:
The sum of the row 1 is: 10
Search x =
x is at a[0][0]
x is at a[1][1]
2
For interactive run, you can remove the newline characters at your wish.