제출 #225293

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
225293		alvinpiter	Mountains (NOI20_mountains)	C++14	100 / 100	338 ms	13168 KiB

Mountains

#include<bits/stdc++.h>
using namespace std;
#define LL long long int
#define MAXN 300000

int N, M;
LL H[MAXN + 3], answer;
int prefix[MAXN + 3], suffix[MAXN + 3]; //BIT
vector<LL> uniqH;

void update(int bit[], int idx, int val) {
    while (idx <= M) {
        bit[idx] += val;
        idx += (idx & -idx);
    }
}

int query(int bit[], int idx) {
    int result = 0;
    while (idx > 0) {
        result += bit[idx];
        idx -= (idx & -idx);
    }

    return result;
}

int id(LL h) {
    return (lower_bound(uniqH.begin(), uniqH.end(), h) - uniqH.begin()) + 1;
}

int main() {
    scanf("%d", &N);
    for (int i = 1; i <= N; i++) {
        scanf("%lld", &H[i]);
        uniqH.push_back(H[i]);
    }

    sort(uniqH.begin(), uniqH.end());
    uniqH.resize(distance(uniqH.begin(), unique(uniqH.begin(), uniqH.end())));

    M = (int) uniqH.size();

    memset(prefix, 0, sizeof(prefix));
    memset(suffix, 0, sizeof(suffix));

    for (int i = 2; i <= N; i++)
        update(suffix, id(H[i]), 1);

    answer = 0;
    for (int i = 2; i < N; i++) {
        update(prefix, id(H[i - 1]), 1);
        update(suffix, id(H[i]), -1);

        int numLeft = query(prefix, id(H[i]) - 1);
        int numRight = query(suffix, id(H[i]) - 1);
        answer += (LL) numLeft * numRight;
    }

    printf("%lld\n", answer);
}

컴파일 시 표준 에러 (stderr) 메시지

Mountains.cpp: In function 'int main()':
Mountains.cpp:33:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &N);
     ~~~~~^~~~~~~~~~
Mountains.cpp:35:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%lld", &H[i]);
         ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12