talking about the algorithm of division and treatment, first of all from the literal meaning of understanding: is to divide a problem into a number of smaller problems of the algorithm. In fact, the meaning of the topic. The basic design idea is to decompose a large problem that is difficult to be solved directly into some of the same small problems in order to conquer, divide and conquer. Design steps: 1) Decomposition: Decomposition into several sub-problems 2) Solving: Solving sub-problems 3) Merging: The solution of the sub-solution is merged into the original problem. in the self-examination, we encountered the two-way merge algorithm belongs to a division method. Of course, to learn the algorithm, we must find its core, grasp its core, we also understand how the algorithm is going on. Below we find its core through the two-way merging algorithm.
Example: Give a column number: 4,2,8,3. The two-way merging algorithm is used to arrange ascending order.
Solution: 1, combining the first two numbers into a small problem, the latter two merged into a small problem: ((4,2) (8,3) can be ((2,4) (3,8 )) 2. ask for their ascending order separately. Then merge the results together to ask for their ascending order. the
key is here: The result of the merge is how to ask in ascending order. It is very simple to compare the minimum values of two results, such as 2 and 3, to find the smallest place in the first position 2, in the remaining 3 and the previous group of the second number compared to 4, get the smallest place to the second position 3. Just like what the teacher said: The two stacks of the Order of Poker, first take out the first one to compare, find a minimum, in the second Zhang and the first comparison of the big comparison. Loop until finished.
Summary: Through the above example, we can find the fundamental idea of the period: two rows of ordered numbers from small to large comparison. The general formula can be written in the following form:
< Span style= "font-size:14pt" > if l[i]<=r[j] then
< Span style= "font-size:14pt" > a[k]=l[i] , i=i+1
< Span style= "font-size:14pt" > else
A[K]=R[J] , j=j+1
Looking back--divide and conquer algorithm
