KMP算法
public static int kmpSearch(String s, String p) {
int sLen = s.length();
int pLen = p.length();
if (sLen < pLen) {
return -1;
}
int[] next = getNext(p);
int i = 0, j = 0;
while (i < sLen && j < pLen) {
if (j == -1 || s.charAt(i) == p.charAt(j)) {
i++;
j++;
} else {
j = next[j];
}
}
if (j == pLen) {
return i - j;
} else {
return -1;
}
}
public static int[] getNext(String p) {
int len = p.length();
int[] next = new int[len];
next[0] = -1;
int i = 0, k = -1;
while (i < len - 1) {
if (k == -1 || p.charAt(i) == p.charAt(k)) {
++k;
++i;
if (p.charAt(i) != p.charAt(k)) {
next[i] = k;
} else {
next[i] = next[k];
}
} else {
k = next[k];
}
}
return next;
}