public String longestCommonPrefix(String[] strs) {
if(strs.length==0) return "";
String str0 = strs[0];
if(str0.length()==0) return "";
int rightMostIndex = str0.length()-1;
for(int k=1;k<strs.length;k++){
for(int i=0;i<=rightMostIndex;i++){
if((i>strs[k].length()-1)||strs[k].charAt(i)!=str0.charAt(i))
rightMostIndex=i-1;
}
}
return rightMostIndex>=0?str0.substring(0,rightMostIndex+1):"";
}