Submission #1315798

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define repq(i,a,n) for(int (i)=(a); (i)<=(n); (i)++)
#define repr(i,a,n) for(int (i)=(a); (i)>=(n); (i)--)
#define int long long
template<typename T> void chmax(T &a, T b) {a = max(a, b);}
template<typename T> void chmin(T &a, T b) {a = min(a, b);}
template<typename T> void chadd(T &a, T b) {a = a + b;}
typedef pair<int, int> pii;
typedef long long ll;
constexpr ll INF = 1001001001001001LL;
constexpr ll MOD = 1000000007LL;

int N, M;

signed main() {
    scanf("%lld%lld", &N, &M);
    // ma[i] := i 番目の区間までの右端の最大値
    vector<pii> es(M);
    vector<int> ma(M);
    rep(i,0,M) {
        int a, b; scanf("%lld%lld", &a, &b);
        es[i] = pii(a, b);
    }
    sort(es.begin(), es.end());
    ma[0] = es[0].second;
    rep(i,1,M) {
        // printf("es[%lld] = (%lld, %lld)\n", i, es[i].first, es[i].second);
        ma[i] = max(ma[i-1], es[i].second);
    }

    int cur = 1, cnt = 0;
    while(1) {
        // 条件を満たす区間の 1 つ先を upper_bound で取得
        int k = upper_bound(es.begin(), es.end(), pii(cur, INF)) - es.begin() - 1;
        if(k < 0 || ma[k] < cur) {
            printf("Impossible\n");
            return 0;
        }

        // 次の cur を決める
        cnt++;
        cur = ma[k] + 1;
        if(cur == N+1) {
            printf("%lld\n", cnt);
            return 0;
        }
        else if(cur > N) assert(false);
    }
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:18:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld%lld", &N, &M);
                              ^
./Main.cpp:23:44: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         int a, b; scanf("%lld%lld", &a, &b);
                                            ^

Judge Result