Submission #1281418

#	Time	Username	Problem	Language	Result	Execution time	Memory
1281418		Kerim	Exam (eJOI20_exam)	C++17	0 / 100	43 ms	98416 KiB

exam

#include "bits/stdc++.h"

using namespace std;
const int N = 1e5+5;
const int K = 5005;
int l[N], r[N], a[N], b[N];
int dp[K][K], n;
int rec(int x, int y){
    if (x > n or y > n)
        return 0;
    int &ret = dp[x][y];
    if (~ret)
        return ret;
    ret = max(rec(x+1, y), rec(x, y+1)); //skip
    if (a[x] == b[y] and l[x] <= y and y <= r[x]) //match
        ret = max(ret, rec(x, y+1) + 1);
    return ret;
}
int main(){
    freopen("file.in", "r", stdin);
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
        scanf("%d", a+i);
    for (int i = 1; i <= n; i++)
        scanf("%d", b+i);
    a[0] = a[n+1] = 2e9;
    stack<int>st;
    //for left
    st.push(0);
    for (int i = 1; i <= n; i++){
        while (!st.empty() and a[st.top()] <= a[i])
            st.pop();
        l[i] = st.top()+1;
        st.push(i);
    }
    //for right
    while (!st.empty())
        st.pop();
    st.push(n+1);
    for (int i = n; i >= 1; i--){
        while (!st.empty() and a[st.top()] <= a[i])
            st.pop();
        r[i] = st.top()-1;
        st.push(i);
    }
    if (n < K){
        memset(dp, -1, sizeof dp);
        printf("%d\n", rec(0, 0));
    }
    else if (count(b+1, b+n+1, b[1]) == n){//subtask 2
        int found = 0, cnt = 0, answer = 0;
        for (int i = 1; i <= n; i++){
            if (a[i] <= b[i]){
                found |= a[i] == b[i];
                cnt += 1;
            }
            else{
                if (found)
                    answer += cnt;
                cnt = found = 0;
            }
        }
        if (found)
            answer += cnt;
        printf("%d\n", answer);
    }
    else
        assert(0);
}

Compilation message (stderr)

exam.cpp: In function 'int main()':
exam.cpp:20:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |     freopen("file.in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
exam.cpp:21:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
exam.cpp:23:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |         scanf("%d", a+i);
      |         ~~~~~^~~~~~~~~~~
exam.cpp:25:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |         scanf("%d", b+i);
      |         ~~~~~^~~~~~~~~~~

• Subtask 1: 0 / 14
• Subtask 2: 0 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 23
• Subtask 5: 0 / 16
• Subtask 6: 0 / 22