Searching an element in 2D sorted matrix

Problem:
Write an efficient program that searches for a value in an n x m sorted matrix. This matrix is sorted along the rows and columns.

Solution:

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bool find(int mat[][], int N, int target) {     if (target < mat[0][0] || target > mat[N-1][N-1])      return false;       int row = 0;   int col = N-1;     while (row <= N-1 && col >= 0) {     if (mat[row][col] < target)       row++;     else if (mat[row][col] > target)       col--;     else       return true;   }   return false; }