For each element , check both elements just below the number and below left to the number add the maximum of them to it
if ( j - 1 >= 0 ) tri [ i , j ] += Math . Max ( tri [ i + 1 , j ] , tri [ i + 1 , j - 1 ] ) ; else tri [ i , j ] += tri [ i + 1 , j ] ; ans = Math . Max ( ans , tri [ i , j ] ) ; } }