单调双端队列 RE#3 求调

#include <cstdio>
#include <deque>
using namespace std;

long long int n,k,a[1000030];
deque<long long int> t;

int main(){
    scanf("%lld%lld",&n,&k);

    for (long long int i = 1;i <= n;i++) scanf("%lld",&a[i]);

    for (long long int i = 1;i <= n;i++){
        if (t.front() == i - k) t.pop_front();
        while (!t.empty()){
            if (a[i] < a[t.back()]) t.pop_back();
            else break;
        }
        t.push_back(i);
        if (i >= k) printf("%lld ",a[t.front()]);
    }

    t.clear();
    printf("\n");

    for (long long int i = 1;i <= n;i++){
        if (t.front() == i - k) t.pop_front();
        while (!t.empty()){
            if (a[i] > a[t.back()]) t.pop_back();
            else break;
        }
        t.push_back(i);
        if (i >= k) printf("%lld ",a[t.front()]);
    }

    return 0;
}

测试点 3 报错（RE）：Received signal 11: Segmentation fault with invalid memory reference.。

尝试了 n=k=1、n>k=1 等特殊情况都没发现问题。