PAT甲級(1057):Stack
ツリー配列参照リンク詳細:ツリー配列詳細
#include
#include
#define lowbit(i) ((i) & (-i))
const int maxn = 100010;
using namespace std;
int c[maxn];
stack<int> s;
void update(int x, int v) {
for(int i = x; i < maxn; i += lowbit(i))
c[i] += v;
}
int getsum(int x) {
int sum = 0;
for(int i = x; i >= 1; i -= lowbit(i))
sum += c[i];
return sum;
}
void PeekMedian() {
int left = 1, right = maxn, mid, k = (s.size() + 1) / 2;
while(left < right) {
mid = (left + right) / 2;
if(getsum(mid) >= k)
right = mid;
else
left = mid + 1;
}
printf("%d
", left);
}
int main() {
int n, temp;
scanf("%d", &n);
char str[15];
for(int i = 0; i < n; i++) {
scanf("%s", str);
if(str[1] == 'u') {
scanf("%d", &temp);
s.push(temp);
update(temp, 1);
} else if(str[1] == 'o') {
if(!s.empty()) {
update(s.top(), -1);
printf("%d
", s.top());
s.pop();
} else {
printf("Invalid
");
}
} else {
if(!s.empty())
PeekMedian();
else
printf("Invalid
");
}
}
return 0;
}