main.java

// divide and conquer

classSolution {
publicStringlongestCommonPrefix(String[] strs) {
if(strs == null || strs.length <= 0) {
return"";
 }

returnlongestCommonPrefixHelper(strs, 0, strs.length - 1);
 }

privateStringlongestCommonPrefixHelper(String[] strs, intleft, intright) {
if(left == right) {
returnstrs[left];
 } else {
intmid = (left + right) / 2;
Stringstr1 = longestCommonPrefixHelper(strs, left, mid);
Stringstr2 = longestCommonPrefixHelper(strs, mid + 1, right);
returncommonPrefix(str1, str2);
 }
 }

privateStringcommonPrefix(Stringstr1, Stringstr2) {
intminimum = Math.min(str1.length(), str2.length());
Stringresult;

for(inti = 0; i < minimum; i++) {
if(str1.charAt(i) != str2.charAt(i)) {
result = str1.substring(0, i);
returnresult;
 }
 }

result = str1.substring(0, minimum);
returnresult;
 }
}