Where is the gamma in codeforces logo?
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Where is the gamma in codeforces logo?
Given an N*N matrix A, whose elements are either 0 or 1. A[i, j] means the number in the i-th row and j-th column. Initially we have A[i, j] = 0 (1 <= i, j <= N).
We can change the matrix in the following way. Given a rectangle whose upper-left corner is (x1, y1) and lower-right corner is (x2, y2), we change all the elements in the rectangle by using "not" operation (if it is a '0' then change it into '1' otherwise change it into '0'). To maintain the information of the matrix, you are asked to write a program to receive and execute two kinds of instructions.
I know this problem can be easily solved by a two-decimal BIT. However, I want a two-decimal segment tree solution. for all day I've been trying to think of it but I failed :(
thanks in advance.
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