题解 | #反转字符串#

利用栈反转字符串，复杂度为O(n)，比较麻烦但也是一种方法
public String solve (String str) {
// write code here
if(str.length() == 0 || "".equals(str)){
return str;
}
Stack stack = new Stack();
String res = "";
char[] ch = str.toCharArray();
for(int i = 0; i < ch.length; i++){
stack.push(ch[i]);
}
while(!stack.isEmpty()){
res = res + ""+stack.pop();
}
return res;
}