Fzu 1752 a ^ B mod C

A ^ B mod C

Time Limit: 1 s	Memory limit: 32 m
Accepted submit: 68	Total submit: 376

Problem description Given a, B, c, you shoshould quickly calculate the result of a ^ B mod C. (1 <= A, B, C <2 ^ 63 ). Input   There are multiply testcases. Each testcase, there is one line contains three integers A, B and C, separated by a single space.   Output   For each testcase, output an integer, denotes the result of a ^ B mod C.   Sample Input 3 2 42 10 1000 Sample output 124 Original: fzu 2009 Summer Training IV -- Number Theory

Solution:

Powerful questions. We need to consider that the data is too large and may overflow during data processing. Collect and repost some good articles on the modulo power operation. In the next article. (The following code can pass fzu 1650, but 1650 of the Code may not pass 1752 .)

# Include <stdio. h> </P> <p> unsigned long MUL (unsigned long a, unsigned long B, unsigned long C) <br/>{< br/> unsigned long ret = 0, TMP = A % C; <br/> while (B) <br/> {<br/> If (B & 0x1) <br/> If (Ret + = TMP)> = C) <br/> ret-= C; <br/> If (TMP <= 1)> = C) <br/> TMP-= C; <br/> B >>= 1; <br/>}< br/> return ret; <br/>}</P> <p> unsigned long Mod (unsigned long a, unsigned long B, unsigned long c) <B R/>{< br/> unsigned long y = 1; <br/> while (B) <br/>{< br/> If (B & 1) <br/> Y = MUL (Y, a, c); <br/> A = MUL (a, a, c ); <br/> B = B> 1; <br/>}< br/> return y; <br/>}</P> <p> int main () <br/>{< br/> unsigned long a, B, c; <br/> while (scanf ("% LlU", &, & B, & C )! = EOF) <br/> printf ("% LlU/N", MOD (A, B, C); <br/> return 0; <br/>}