Loves Me?, Loves Me Not?

What makes us fall in love?

We all have a template for the ideal partner buried somewhere in our subconscious. It is this love map that decides which person in that crowded room catches our eye. But how is this template formed?

Appearance
Many researchers have speculated that we tend to go for members of the opposite sex who remind us of our parents. Some have even found that we tend to be attracted to those who remind us of ourselves. In fact, cognitive psychologist David Perrett, at the University of St. Andrews in Scotland, did an experiment in which he morphed a digitized photo of the subject's own face into a face of the opposite sex. Then, he had the subject select from a series of photos which one he or she found most attractive. According to Dr. Perrett, his subjects always preferred the morphed version of their own face (and they didn't recognize it as their own).

Personality
Like appearance, we tend to form preferences for those who remind us of our parents (or others close to us through childhood) because of their personality, sense of humor, likes and dislikes, etc.

Pheromones
The debated topic of human pheromones still carries some weight in the field of love research. The word "pheromone" comes from the Greek words pherein and hormone, meaning "excitement carrier".

In the animal world, pheromones are individual scent "prints" found in urine or sweat that dictate sexual behavior and attract the opposite sex. They help animals identify each other and choose a mate with an immune system different enough from their own to ensure healthy offspring. They have a special organ in their noses called the vomeronasal organ (VNO) that detects this odorless chemical.

The existence of human pheromones was discovered in 1986 by scientists at the Chemical Senses Center in Philadelphia and its counterpart in France. They found these chemicals in human sweat. A human VNO has also been found in some, but not all, people. Even if the VNO isn't present in all of us -- and may not be working in those who do have it -- there is still evidence that smell is an important aspect of love (note the booming perfume industry). An experiment was conducted where a group of females smelled the unwashed tee shirts of a group of sweaty males, and each had to select the one to whom she was most "attracted." Just like in the animal world, the majority of the females chose a shirt from the male whose immune system was the most different from their own.

SUDOKU?

Lets explore the game of Sudoku.
You Know;
The name "Sudoku" is the Japanese abbreviation of a longer phrase, "Sūji wa dokushin ni kagiru", meaning "the digits must occur only once. The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are irrelevant. Any set of distinct symbols will do; letters, shapes, or colours may be used without altering the rules. The attraction of the puzzle is that the rules are simple, yet the line of reasoning required to solve the puzzle may be complex.
The strategy for solving a puzzle may be regarded as comprising a combination of three processes: scanning, marking up, and analyzing.
1) Scanning:
Scanning is performed at the outset and throughout the solution. Scans need to be performed only once in between analyses. Scanning consists of two techniques:
a) Cross-hatching: the scanning of rows to identify which line in a region may contain a certain numeral by a process of elimination. The process is repeated with the columns. For fastest results, the numerals are scanned in order of their frequency, from high to low. It is important to perform this process systematically, checking all of the digits 1–9.
b) Counting 1–9 in regions, rows, and columns to identify missing numerals. Counting based upon the last numeral discovered may speed up the search. It also can be the case, particularly in tougher puzzles, that the best way to ascertain the value of a cell is to count in reverse—that is, by scanning the cell's region, row, and column for values it cannot be, in order to see what remains.
Advanced solvers look for "contingencies" while scanning, narrowing a numeral's location within a row, column, or region to two or three cells. When those cells lie within the same row and region, they can be used for elimination during cross-hatching and counting. Puzzles solved by scanning alone without requiring the detection of contingencies are classified as "easy"; more difficult puzzles cannot be solved by basic scanning alone.
2) Marking up:
Scanning stops when no further numerals can be discovered, making it necessary to engage in logical analysis. One method to guide the analysis is to mark candidate numerals in the blank cells. There are two popular notations: subscripts and dots.

a) In the subscript notation the candidate numerals are written in subscript in the cells. Because puzzles printed in a newspaper are too small to accommodate more than a few subscript digits of normal handwriting, solvers may create a larger copy of the puzzle.
b) The second notation uses a pattern of dots in each square, where the dot position indicates a number from 1 to 9. The dot notation can be used on the original puzzle. Dexterity is required in placing the dots, since misplaced dots or inadvertent marks inevitably lead to confusion and may not be easily erased.

An alternative technique is to "mark up" the numerals that a cell cannot be. A cell will start empty and as more constraints become known, it will slowly fill until only one mark is missing. Assuming no mistakes are made and the marks can be overwritten with the value of a cell, there is no longer a need for any erasures.

3) Analysis:
The two main approaches to analysis are "candidate elimination" and "what-if". In "candidate elimination", progress is made by successively eliminating candidate numerals from cells to leave one choice. After each answer has been achieved, another scan may be performed—usually checking to see the effect of the contingencies. In general, if entering a particular numeral prevents completion of the other necessary placements, then the numeral in question can be eliminated as a candidate. One method works by identifying "matched cell groups". For instance, if precisely two cells within a scope (a particular row, column, or region) contain the same two candidate numerals (p,q), or if precisely three cells within a scope contain the same three candidate numerals (p,q,r), these cells are said to be matched. The placement of those candidate numerals anywhere else within that same scope would make a solution impossible; therefore, those candidate numerals can be deleted from all other cells in the scope.

In the "what-if" approach (also called "guess-and-check", "bifurcation", "backtracking" and "Ariadne's thread"), a cell with two candidate numerals is selected, and a guess is made. The steps are repeated unless a duplication is found or a cell is left without a possible candidate, in which case the alternative candidate must be the solution. For each cell's candidate, the question is posed: 'will entering a particular numeral prevent completion of the other placements of that numeral?' If the answer is 'yes', then that candidate can be eliminated. The what-if approach requires a pencil and eraser or a good layout memory.

There are three kind of conflicts, which can appear during puzzle solving:

basic conflicts - there are only N-1 different candidates in N cell in the area
fish conflicts - when eliminating number from N rows/columns, it will disappear also from N+1 columns/rows.
unique conflicts - this pattern means multiple solutions, all numbers in the pattern exist exactly two times in every area, row and column. If there are only one candidate in the cell, any virtual candidate can be added.