# java 实现的Boyer-Moore(BM)算法

BM算法是一种高效的单模查找算法，可以加大查找步长，效率很高, 这是java实现的版本

```    import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;

public class BoyerMoore {
public static List<Integer> match(String pattern, String text) {
List<Integer> matches = new ArrayList<Integer>();
int m = text.length();
int n = pattern.length();
int alignedAt = 0;
while (alignedAt + (n - 1) < m) {
for (int indexInPattern = n - 1; indexInPattern >= 0; indexInPattern--) {
int indexInText = alignedAt + indexInPattern;
char x = text.charAt(indexInText);
char y = pattern.charAt(indexInPattern);
if (indexInText >= m) break;
if (x != y) {
Integer r = rightMostIndexes.get(x);
if (r == null) {
alignedAt = indexInText + 1;
}
else {
int shift = indexInText - (alignedAt + r);
alignedAt += shift > 0 ? shift : 1;
}
break;
}
else if (indexInPattern == 0) {
alignedAt++;
}
}
}
return matches;
}
String pattern) {
Map<Character, Integer> map = new HashMap<Character, Integer>();
for (int i = pattern.length() - 1; i >= 0; i--) {
char c = pattern.charAt(i);
if (!map.containsKey(c)) map.put(c, i);
}
return map;
}
public static void main(String[] args) {
List<Integer> matches = match("ana", "bananas");
for (Integer integer : matches) System.out.println("Match at: " + integer);
System.out.println((matches.equals(Arrays.asList(1, 3)) ? "OK" : "Failed"));
}
}
```

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