查找字符串数组中的最长公共前缀。
纵向扫描：
public String longestCommonPrefix(String[] strs) {
if (strs == null || strs.length==0)
return "";
String result = "";
int minLength = strs[0].length();
for (String st : strs ){
if (st.length()<minLength) {
minLength = st.length();
}
}
for (int i = 0; i < minLength; i++) {
char c = strs[0].charAt(i);
for (String s :strs) {
if (s.charAt(i) != c ){
return result;
}
}
result += c;
}
return result;
}
