字符串Hash

typedef long long ll;
typedef unsigned long long ull;
const int MAGIC = 131;

long long h[N], base[N];
long long MOD = (long long)1e9 + 7;

inline void Hash(char *s) {
	int l = strlen(s);
	h[0] = 1;
	for (int i = 1; i <= l; ++i) h[i] = (h[i - 1] * MAGIC % MOD + s[i - 1] - 'a') % MOD;
	base[0] = 1;
	for (int i = 1; i <= l; ++i) base[i] = (base[i - 1] * MAGIC) % MOD;
}

inline long long get(int l, int r) {
	return (h[r] - h[l - 1] * base[r - l + 1] % MOD + MOD) % MOD;
}

原文：http://blog.csdn.net/qq574857122/article/details/44905101