Checking the common elements in a row of a matrix

Author: divyaachoudharyy

General Questions/Common_elements_in_all_rows_of_a_given_matrix.cpp

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+/******************************************************************************
+
+Given an m x n matrix, find all common elements present in all rows in one traversal of matrix.
+
+*******************************************************************************/
+
+//SOLUTION (in C++)
+
+#include <bits/stdc++.h>
+
+using namespace std;
+#define M 4
+#define N 5
+
+
+void printCommonElements(int arr[M][N])
+{
+    int i, j;
+    //we'll use a amp to store the count of common numbers in a rows
+    unordered_map<int, int> m;
+    
+    //since, we need to find common elements, it is completely dependent on the first row of the Matrix
+    //initially all the 1st row elements count will be 1, even if they contain duplicates
+    for(i = 0;i<N;i++)
+       m[arr[0][i]] = 1;
+       
+    //traverse the matrix
+    for(i = 1;i<M;i++)
+    {
+        for(j = 0;j<N;j++)
+        {
+            
+            //for any row, my element's freq should be equal to the previous row's number, 
+            //if it is, then there is high chance that it can be common and we;'' increase the count.
+            //we are ignoring the elements whose gfreq count is not equal to the row, so it reduces our work
+            if(m[arr[i][j]] == i){
+                m[arr[i][j]]++;
+
+                //if the freq of the element in the row becomes equal to the no. of rows,
+               //then it means it is coming in all rows and is the common element.
+                if(m[arr[i][j]] == M){ 
+                   cout<<arr[i][j]<<" ";
+                }
+            }
+        }
+    }
+}
+
+int main()
+{
+    cout<<"Matrix"<<endl;
+    int mat[M][N] =
+    {
+        {1, 2, 3, 1, 8},
+        {3, 7, 8, 5, 1},
+        {8, 7, 7, 3, 1},
+        {8, 1, 2, 3, 9},
+    };
+    cout<<"Common eleemnts of each row"<<endl;
+    printCommonElements(mat);
+    return 0;
+}