KMP 字符串匹配

public class KMPProcess {
	public static void buildNext(String str, int[] next) {	
		if (str == null || next == null || str.length() != next.length) 
			throw new IllegalArgumentException();
		
		int i = 0; 
		int k;
		
		next[i] = k = -1;
		
		while (i < str.length() - 1) {
			if (k == -1 || str.charAt(i) == str.charAt(k)) {
				i ++;
				k ++;
				next[i] = k;
			} else {
				k = next[k];
			}
		}	
	}
	
	public static void main(String[] args) {
		String target = "dabc";
		String source = "acdfffabcafdddabcac";
		
		int[] next = new int[target.length()];
		buildNext(target, next);

		int sourceIndex = 0;
		int targetIndex = 0;
		
		while (sourceIndex < source.length() && targetIndex < target.length() ) {
			if (source.charAt(sourceIndex) == target.charAt(targetIndex)) {
				sourceIndex ++;
				targetIndex ++;
			} else if (targetIndex == 0) {
				sourceIndex ++;
			} else {
				targetIndex = next[targetIndex];
				System.out.println("targetIndex=" + targetIndex);
			}
		}
		
		System.out.println("source length = " + source.length() +  "     ,  sourceIndex = " + sourceIndex);
		System.out.println("target length = " + target.length() +  "     ,  targetIndex = " + targetIndex);
		
		if (targetIndex == target.length()) {
			System.out.println("index : " + (sourceIndex - target.length()));
		}
	}
	
}