两个栈实现队列
private List<String> mStack1 = new ArrayList<>();
private List<String> mStack2 = new ArrayList<>();
private void appendTail(String str) {
mStack1.add(str);
}
private String deleteHead() {
if(mStack1.size() > 0) {
for(int i = mStack1.size()-1; i >= 0; --i) {
mStack2.add(mStack1.get(i));
mStack1.remove(i);
}
}
if (mStack2.size() == 0)
return null;
int last = mStack2.size()-1;
String head = mStack2.get(last);
mStack2.remove(last);
return head;
}
两个队列实现栈
private List<String> mStack1 = new ArrayList<>();
private List<String> mStack2 = new ArrayList<>();
private void appendTail(String str) {
mStack1.add(str);
}
private String deleteHead() {
String head = null;
if(mStack1.size() > 1) {
while(mStack1.size() > 1) {
mStack2.add(mStack1.get(0));
mStack1.remove(0);
}
}
if(mStack1.size() == 1) {
head = mStack1.get(0);
mStack1.clear();
return head;
}
if(mStack2.size() > 1) {
while(mStack2.size() > 1) {
mStack1.add(mStack2.get(0));
mStack2.remove(0);
}
}
if(mStack2.size() == 1) {
head = mStack2.get(0);
mStack2.clear();
return head;
}
return null;
}
