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字符串匹配算法之Sunday算法

2015.04.09 尤淇  热度 ℃

Sunday Algorithm

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/**
 * sunday字符串匹配算法
 * @param text 目标串
 * @param pattern 模式串
 * @return 返回模式串在目标串中出现的起始位置，不存在返回-1
 */
public int sunday(String text, String pattern){
	int patternLen = pattern.length();
	int textLen = text.length();
	
	int i = 0;
	int j = 0;
	
	while(i < textLen && j < patternLen){
		if(text.charAt(i) == pattern.charAt(j)){
			i++;
			j++;
		}else{
			if(i + patternLen >= textLen)
				break;
			
 				int k = isContains(pattern, text.charAt(i+patternLen));
			if(k == -1)
				i = i + patternLen;
			else
				i = i + patternLen - k;
			
			j = 0;
		}
	}

	if(j == patternLen)
		return i - j;
	else
		return -1;
}

private int isContains(String pattern, char next){
	for(int i = 0; i < pattern.length(); i++){
		if(next == pattern.charAt(i))
			return i;
		
	}
	return -1;
}