BZOJ 3555 CTSC 2014 Penguin QQ Hash

To distinguish the qq accounts from the accounts of a person, we need to write a program to determine which names are similar. Similar definitions mean that there are different characters with only one position.

Idea: The data range is not too large. It is obvious that Hash is not used for binary. I heard from my teacher that one of the students who took the CTSC test this year did not answer this question because they thought too much. He wrote the Hash at the time, and then he had nothing to do. He had a set of data cards and lost his hash, and then he did not dare to hand in the hash. Finally, he handed in a Trie tree and the result was T .. The lessons of blood tell us not to think too much ..

Preprocessing each string first to obtain the hash value. Then enumerate each bit. In the O (1) time, obtain the Hash removed from this bit, and then judge the weight. I wanted to hand-write the hash table. After reading the online question solution, I found that the problem could be solved quickly...

CODE:

# Include <cstdio> # include <cstring> # include <iostream> # include <algorithm> # define MAX 30010 # define BASE 137 using namespace std; int points, length; char src [MAX] [210]; unsigned long hash [MAX] [210], power [MAX]; unsigned long _ hash [MAX]; void Pretreatment () {power [0] = 1; for (int I = 1; I <= length; ++ I) power [I] = power [I-1] * BASE ;} inline void GetHash (char * s, unsigned long hash []) {for (int I = 1; I <= length; ++ I) hash [I] = hash [I-1] * BASE + s [I];} inline unsigned long CalcHash (unsigned long hash [], int I) {unsigned long re = hash [length]; re = re-hash [I] * power [length-I] + hash [I-1] * power [length-I + 1]; return re;} int main () {scanf ("% d % * d", & points, & length); Pretreatment (); for (int I = 1; I <= points; ++ I) {scanf ("% s", src [I] + 1); GetHash (src [I], hash [I]);} int ans = 0; for (int I = 1; I <= length; ++ I) {for (int j = 1; j <= points; ++ j) _ hash [j] = CalcHash (hash [j], I); sort (_ hash + 1, _ hash + points + 1 ); _ hash [points + 1] = 0; int start = 1; for (int j = 1; j <= points + 1; ++ j) if (_ hash [j]! = _ Hash [start]) {int cnt = j-start; ans + = cnt * (cnt-1)> 1; start = j ;}} cout <ans <endl; return 0 ;}

BZOJ 3555 CTSC 2014 Penguin QQ Hash