ZOJ Problem Set - 1388
Given n integer registers r1, r2, ..., rn we define a Compare-Exchange Instruction CE(a, b), where a, b are register indices (1 <= a < b <= n):
A Compare-Exchange program (shortly CE-program) is any nite sequence of Compare-Exchange instructions. A CE-program is called a Minimum-Finding program if after its execution the register r1 always contains the smallest value among all values in the registers. Such program is called reliable if it remains a Minimum-Finding program after removing any single Compare-Exchange instruction.
Given a CE-program P , what is the smallest number of instructions that should be added at the end of program P in order to get a reliable Minimum-Finding program?
CE(1, 2); CE(2, 3); CE(1, 2).
reads the description of a CE-program,
computes the smallest number of CE-instructions that should be added to make this program a reliable Minimum-Finding program,
writes the result.
Each data set consists of exactly two consecutive lines.
The first of those lines contains exactly two integers n and m separated by a single space, 2 <= n <= 10 000, 0 <= m <= 25 000. Integer n is the number of registers and integer m is the number of program instructions.
The second of those lines contains exactly 2m integers separated by single
spaces - the program
Line i, 1 <= i <= d, should contain only one integer - the smallest number of instructions that should be added at the end of the i-th input program in order to make this program a reliable Minimum-Finding program.
Source: Central Europe 2001