42 lines
1.5 KiB
C++
42 lines
1.5 KiB
C++
/*
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Rabin_Karp：虽说用KMP更好，但是RK算法好理解。简单说一下RK算法的原理：首先把模式串的哈希值算出来，
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在文本串里不断更新模式串的长度的哈希值，若相等，则找到了，否则整个模式串的长度的哈希值向右移动一位
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*/
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#include <bits/stdc++.h>
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using namespace std;
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typedef unsigned long long ULL;
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const int N = 1e4 + 10;
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const int M = 1e6 + 10;
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const ULL KEY = 100000007;
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int s[M], p[N];
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int n, m;
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int match() {
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ULL h = 1;
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for (int i = 0; i < n; i++) h *= KEY;
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//对齐0~n-1
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ULL ah = 0, bh = 0;
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for (int i = 0; i < n; i++) ah = ah * KEY + s[i]; //模拟成KEY进制，然后利用ULL溢出的形式，相当于对2^64取模
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for (int i = 0; i < n; i++) bh = bh * KEY + p[i];
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//开始尝试匹配
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for (int i = 0; i <= m - n; i++) {
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if (ah == bh) return i + 1; //如果HASH值一致，则返回匹配位置，因本题要求数组下村从1开始，所以+1后返回
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if (i < m - n) ah = ah * KEY + s[i + n] - s[i] * h; //怕越界，因为数据弱，不写if也能AC，但如果模式串最后一位是0，就狒狒了，原因看EXCEL
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}
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return -1;
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}
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int main() {
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int T;
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scanf("%d", &T);
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while (T--) {
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scanf("%d%d", &m, &n);
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for (int i = 0; i < m; i++) scanf("%d", &s[i]); //源串
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for (int i = 0; i < n; i++) scanf("%d", &p[i]); //模式串
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printf("%d\n", match());
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}
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return 0;
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} |