(c++) 백준 "15829)Hashing"

https://www.acmicpc.net/problem/15829

15829번: Hashing

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#include <iostream>
#include <cmath>
#include <string>
#define mod 1234567891LL;
using namespace std;
int main() {
	int N; cin >> N;
	string str; cin >> str;
	unsigned long hash = 0;
	unsigned long mul = 1;
	for (int i = 0; i < N; i++) {
		long long tmp = (str[i] - 'a' + 1);
		tmp *= mul;
		tmp %= mod;
		hash += tmp;
		mul *= 31;
		mul %= mod;
	}
	hash %= mod;
	cout << hash << endl;
	return 0;
}