14. longest common prefix

所有字符串的最长公共前缀是任意两个字符串的最长公共前缀的子串

//手动匹配前缀
public String longestCommonPrefix(String[] strs) {
        if(strs.length == 0) return "";
        String prefix = strs[0];
        int minlength,j;
        for(int i = 1 ; i < strs.length ; i++){
            String str = strs[i];
            minlength = prefix.length() > str.length() ? str.length() : prefix.length();
            for(j = 0 ; j < minlength ; j++){
                if(prefix.charAt(j) != str.charAt(j)){
                    break;
                }
            }
            if(j==0) {
                prefix = "";
                break;
            }
            prefix = prefix.substring(0,j);
        }
        return prefix;
    }
    
//直接使用java函数
public String longestCommonPrefix(String[] strs) {
        if(strs == null || strs.length == 0)   return "";
        String prefix = strs[0];
        if(strs.length == 1)   return prefix;
        for(int i=1; i<strs.length; i++) {
            while(strs[i].indexOf(prefix)!=0) {
                prefix = prefix.substring(0,prefix.length()-1);
            }
        }
        return prefix;
    }