Submission #7121405

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
using LL = long long; using PII = pair<LL, LL>; using VI = vector<LL>; using VVI = vector<VI>;
using VB = vector<bool>; using VS = vector<string>; using VP = vector<PII>;
#define VV(T)        vector<vector<T>>
#define PB           push_back
#define MP           make_pair
#define SZ(a)        LL((a).size())
#define EACH(x, c)   for (auto x : (c))
#define ALL(c)       (c).begin(), (c).end()
#define REVERSE(c)   reverse(ALL(c))
#define SORT(c)      stable_sort(ALL(c))
#define RSORT(c)     stable_sort((c).rbegin(), (c).rend())
#define FOR(i, a, b) for (LL i = (a); i < (b); ++i)
#define REP(i, n)    FOR(i, 0, n)
#define $(x)         {cout << #x << " = " << (x) << endl;}

const LL MOD = 1000000007;
inline LL mod_add(LL a, LL b) { return (a + b) % MOD; }
inline LL mod_sub(LL a, LL b) { return (a + MOD - b) % MOD; }
inline LL mod_mul(LL a, LL b) { return ((a % MOD) * (b % MOD)) % MOD; }
LL mod_bipow(LL x, LL y) {   // x^y by bisection method
    if (y == 0) return 1;
    else if (y == 1) return x % MOD;
    else if (y % 2 == 0) {
        LL val = mod_bipow(x, (LL)(y / 2));
        return mod_mul(val, val);
    } else {
        LL val = mod_bipow(x, (LL)(y / 2));
        return mod_mul(mod_mul(val, val), x);
    }
}
LL mod_inv(LL x) { return mod_bipow(x, MOD - 2); }   // x^{-1} = x^{MOD-2} (MOD: prime number)
LL mod_div(LL a, LL b) { return mod_mul(a, mod_inv(b)); }   // a/b = a*b^{-1}

void solve(LL N, LL K, vector<LL> A){
    LL ans = 0;
    LL cl = mod_div(mod_mul(mod_sub(K, 1), K), 2);
    LL cr = mod_div(mod_mul(K, mod_add(K, 1)), 2);
    //$(cl);
    //$(cr);
    REP(i, N) {
        LL left = 0, right = 0;   // smaller than A[i]
        REP(j, i) {
            if (A[j] < A[i]) left++;
        }
        FOR(j, i + 1, N) {
            if (A[i] > A[j]) right++;
        }
        //$(left);
        //$(right);
        ans = mod_add(ans, mod_add(mod_mul(cr, right), mod_mul(cl, left)));
    }
    cout << ans << endl;
}

int main(){
    LL N;
    scanf("%lld",&N);
    LL K;
    scanf("%lld",&K);
    vector<LL> A(N-1-0+1);
    for(int i = 0 ; i < N-1-0+1 ; i++){
        scanf("%lld",&A[i]);
    }
    solve(N, K, move(A));
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:59:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld",&N);
                     ^
./Main.cpp:61:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld",&K);
                     ^
./Main.cpp:64:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         scanf("%lld",&A[i]);
                            ^

Judge Result