CODEWITHSUNDEEP
c++arrays
JU-SethY
JU-SethY

Reputation: 31

Program to search if a number is contained in a 3x3 array only finds the last number

/--- search.cpp ----------------------------------------------------- Program to read a 3 X 3 matrix of integers mat and an integer item, and search mat to see if it contains item. --------------------------------------------------------------------/

So in this activity we made a program to search a if a number is contained in a 3x3 array.

If I put in 1 2 3 4 5 6 7 8 9 as the elements of the array,

the only number it finds is 9

#include <iostream>
using namespace std;

const int SIZE = 3;               // Set matrix size
//typedef int Matrix[SIZE][SIZE];   // Define data type Matrix

bool matrixSearch(int mat[SIZE][SIZE], int n, int item);

int main()
{
    // Enter the matrix
    int mat[SIZE][SIZE];
    cout << "Enter the elements of the " << SIZE << " X " << SIZE 
        << " matrix rowwise:\n";

    for (int i = 0; i < SIZE; i++)

        for (int j = 0; j < SIZE; j++) 

            cin >> mat[i][j];

    // Search mat for various items
    int itemToFind;
    char response;
    do
    {
        cout << "Enter integer to search for: ";
        cin >> itemToFind;
        if (matrixSearch(mat, SIZE, itemToFind))
            cout << "item found\n";
        else
            cout << "item not found\n";
        cout << "\nMore items to search for (Y or N)? ";
        cin >> response;
    }
    while (response == 'Y' || response == 'y');
}


bool matrixSearch(int mat[SIZE][SIZE], int n, int item) {
    bool found;  
    int col, row;

    for (row = 0; row <n; row++)
        for (col = 0; col < n; col++)  
            if (mat[row][col] == item) {
                found = true;
            }
            else
                found = false;
    return found;
}

Upvotes: 0

Views: 310

Answers (2)

Wander3r
Wander3r

Reputation: 1881

Because, the loop is not breaking, once the item is found. The loop continues to search for the item and changes found to be false again, unless it's the last item.

bool matrixSearch(int mat[SIZE][SIZE], int n, int item) {

   bool found = false; //initialize here 
   int col, row;

   for (row = 0; row < n && !found; row++)
     for (col = 0; col < n; col++)

       if (mat[row][col] == item) {
         found = true; // once found, break the loop
         break;
       }

   return found;
 }

Upvotes: 0

Waqar
Waqar

Reputation: 9331

You set found to false if an item is not a match:

    for (col = 0; col < n; col++)  
      if (mat[row][col] == item)  // if match, set found = true
        found = true;
      else
        found = false;           // otherwise false

So suppose you are searching for item = 4 and the array is 1 2 3 4 5 6 7 8 9. It will find 4 correctly and set found to true. But then the next element will be 5 and since it is not a match, found will be set to false.

To fix simply return from your function when the item is a match:

bool matrixSearch(int mat[SIZE][SIZE], int n, int item)
{
    int col, row;
    for (row = 0; row <n; row++) {
        for (col = 0; col < n; col++) {
            if (mat[row][col] == item)
               return true;             //end function and return true
        }
    }
    return false;   //we got here, that means item was not found, return false
}

Upvotes: 1

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