package algorithm;
class Kmp{
public int index(String a, String b){
if(a == null || b == null || a.length() < b.length())
return -1;
int temp ;
for(int i = 0, j = 0; i < a.length();){
temp = i;
if(a.charAt(i) == b.charAt(j)){
i++;
j++;
if(j == b.length()){
return i - b.length();
}
}else{
i = temp + 1;
j = 0;
}
}
return -1;
}
public int violentmatch(String a, String b){
int alen = a.length();
int blen = b.length();
int i = 0;
int j = 0;
while(i < alen && j < blen){
if(a.charAt(i) == b.charAt(j)){
i++;
j++;
}else{
i = i - j + 1;
j = 0;
}
}
if(j == blen)
return i - j;
return -1;
}
public void getnext(String des, int next[]){
int blen = des.length();
int k = -1; //前缀
int j = 0; //后缀
next[j] = k;
while(j < blen - 1){
if(k == -1 || des.charAt(j) == des.charAt(k)){
j++;
k++;
next[j] = k;
}else{
k = next[k];
}
}
}
public void getnextval(String des, int next[]){
int blen = des.length();
int k = -1;
int j = 0;
next[j] = k;
while(j < blen - 1){
if(k == -1 || des.charAt(j) == des.charAt(k)){
k++;
j++;
if(des.charAt(j) != des.charAt(k))
next[j] = k;
else
next[j] = next[k];
}else{
k = next[k];
}
}
}
public int kmpSearch(String src, String des){
int next[] = new int[des.length()+1];
// getnext(des, next);
getnextval(des, next);
int alen = src.length();
int blen = des.length();
int i = 0;
int j = 0;
while(i < alen && j < blen){
if(j == -1 || src.charAt(i) == des.charAt(j)){
i++;
j++;
}else{
j = next[j];
}
}
if(j == blen)
return i - j;
return -1;
}
//BM算法主函数
public int bmSearch(char[] src, char[] des){
if(des.length == 0)
return 0;
int[] charTable = makeCharTable(des);
int[] gsTable = makeGsTable(des);
int i = 0, j;
while(i <= src.length - des.length){
for(j = des.length - 1; j >= 0 && des[j] == src[j + i]; j--)
if(j == 0)
return i;
i += Math.max(gsTable[j], charTable[src[i]] - (des.length - 1 - j));
}
return -1;
}
//BM算法主函数2
public int bmsearch2(char[] src, char[] des){
int[] charTable = makeCharTable(des);
int[] gsTable = makeGsTable(des);
for(int i = des.length - 1, j; i < src.length;){
for(j = des.length - 1; j >= 0 && src[i] == des[j]; i--, j--)
if(j == 0)
return i;
i += Math.max(gsTable[j], charTable[src[i]] - (des.length - 1 - j));
}
return -1;
}
//模式串预处理
//坏字符规则
public int[] makeCharTable(char[] des){
int[] table = new int[256];
for(int i = 0; i < 256; i++)
table[i] = des.length;
for(int i = 0; i < des.length - 1; i++)
table[des[i]] = des.length - 1 - i;
return table;
}
//好后缀规则
public int[] makeSuffixTable(char[] des){
int suffix[] = new int[des.length];
suffix[des.length - 1] = des.length;
for(int i = des.length - 2; i >= 0; i--){
int q = i;
while(q >= 0 && des[q] == des[des.length - 1 -(i - q)])
q--;
suffix[i] = i - q;
}
return suffix;
}
//good suffix table
public int[] makeGsTable(char des[]){
int i, j, suffix[] = makeSuffixTable(des);
int gs[] = new int[des.length];
//没有匹配好后缀，找不到最大前缀
for(i = 0; i < des.length; i++)
gs[i] = des.length;//好后缀数组初始化
j = 0;
//没有匹配好后缀，但是找到最大前缀
for(i = des.length -1; i >= 0; i--)
if(suffix[i] == i+1) //找到一个最大前缀
for(; j < des.length - 1 - i; j++)
if(gs[j] == des.length)
gs[j] = des.length - 1 - i;
//模式串中有子串匹配上好后缀
for(i = 0; i <= des.length - 2; i++)
gs[des.length - 1 - suffix[i]] = des.length - 1 - i;
return gs;
}
public int sundaySearch(char[] src, char[] des){
int i = 0, j = 0;
int temp, offset;
int[] charTable = makeCharTable(des);
while(i < src.length && j < des.length){
temp = i;
while(src[i] == des[j]){
i++;
j++;
if(j == des.length)
return temp;
}
offset = charTable[src[temp + des.length]] + 1;
i += offset;
j = 0;
}
return -1;
}
}
public class KMP1 {
/*public static int indexOf(char[] haystack, char[] needle) { if (needle.length == 0) { return 0; } int charTable[] = makeCharTable(needle); int offsetTable[] = makeOffsetTable(needle); System.out.println("CharTable: "); for(int t1 : charTable){ System.out.print(t1 + " "); } System.out.println(); System.out.println("OffSetTable: "); for(int t2 : offsetTable){ System.out.print(t2 + " "); } System.out.println(); for (int i = needle.length - 1, j; i < haystack.length;) { for (j = needle.length - 1; needle[j] == haystack[i]; --i, --j) { if (j == 0) { System.out.println("匹配成功 位置 i = "); return i; } } // i += needle.length - j; // For naive method i += Math.max(offsetTable[needle.length - 1 - j], charTable[haystack[i]]); } return -1; } *//** * Makes the jump table based on the mismatched character information. *//* private static int[] makeCharTable(char[] needle) { final int ALPHABET_SIZE = 256; int[] table = new int[ALPHABET_SIZE]; for (int i = 0; i < table.length; ++i) { table[i] = needle.length; } for (int i = 0; i < needle.length - 1; ++i) { table[needle[i]] = needle.length - 1 - i; } return table; } *//** * Makes the jump table based on the scan offset which mismatch occurs. *//* private static int[] makeOffsetTable(char[] needle) { int[] table = new int[needle.length]; int lastPrefixPosition = needle.length; for (int i = needle.length - 1; i >= 0; --i) { if (isPrefix(needle, i + 1)) { lastPrefixPosition = i + 1; } table[needle.length - 1 - i] = lastPrefixPosition - i + needle.length - 1; } for (int i = 0; i < needle.length - 1; ++i) { int slen = suffixLength(needle, i); table[slen] = needle.length - 1 - i + slen; } return table; } *//** * Is needle[p:end] a prefix of needle? *//* private static boolean isPrefix(char[] needle, int p) { for (int i = p, j = 0; i < needle.length; ++i, ++j) { if (needle[i] != needle[j]) { return false; } } return true; } *//** * Returns the maximum length of the substring ends at p and is a suffix. *//* private static int suffixLength(char[] needle, int p) { int len = 0; for (int i = p, j = needle.length - 1; i >= 0 && needle[i] == needle[j]; --i, --j) { len += 1; } return len; }*/
public static void main(String[] args) {
Kmp k = new Kmp();
String src = "ABCGDETYIBCDEKKWSBCDE";
// String src = "BCDE";
String des = "BCDE";
int pos1 = k.index(src, des);
int pos2 = k.violentmatch(src, des);
int kmppos = k.kmpSearch(src, des);
int bmpos = k.bmSearch(src.toCharArray(), des.toCharArray());
int bmpos2 = k.bmsearch2(src.toCharArray(), des.toCharArray());
int sundaypos = k.sundaySearch(src.toCharArray(), des.toCharArray());
System.out.println("String.indexOf(): " + src.indexOf(des));
System.out.println("模式匹配1：" + pos1);
System.out.println("模式匹配2：" + pos2);
System.out.println("kmp: " + kmppos);
System.out.println("my bm: " + bmpos);
System.out.println("my bm 2 : "+ bmpos2);
System.out.println("sunday: " + sundaypos);
// System.out.println("BM other："+ indexOf(src.toCharArray(), des.toCharArray()));
}
}
kmp bm sunday 字符串查找算法
原文作者：KMP算法
原文地址: https://blog.csdn.net/ok0011/article/details/46518381
本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
原文地址: https://blog.csdn.net/ok0011/article/details/46518381
本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
