28. Implement strStr()

String相等 == 只是比较引用值就是地址
如果是new String的话 例如substring跟其他的比较就要用str.equal()

 

 

class Solution {
    public int strStr(String haystack, String needle) {
        if(needle == null) return 0;
        if(haystack.length() < needle.length()) return -1;
        int nlen = needle.length();
        int res = -1;
        for(int i = 0; i < haystack.length() - nlen + 1; i++) {
            if(needle.equals(haystack.substring(i, i+nlen))) {
                return i;
            }
        }
        return res;
        
    }
}