[Offer收割]编程练习赛67

A.序列

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL mod = 1e9 + 7;

int main() {
    int n, p;
    scanf("%d %d", &n, &p);
    if(n >= p) puts("0");
    else {
        LL ans = 1;
        for(int i = 1; i <= n; ++i) ans = ans * (p - i) % mod;
        printf("%lld
", ans);
    }
    return 0;
}

B.彩球

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

__int128 qpow(__int128 a, __int128 b, __int128 mod) {
    __int128 ret = 1LL;
    while (b) {
        if (b & 1) ret = ret * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return ret;
}

int main() {
    LL n, k, P;
    scanf("%lld %lld %lld", &n, &k, &P);
    LL ans = qpow(k, n, P);
    printf("%lld
", ans);
    return 0;
}

C.最优子段

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL INF = 1e18;
const int maxn = 1e6 + 10;
LL a[maxn], sum[maxn];
set<LL> S;

int main() {
    int n, A, B;
    scanf("%d %d %d", &n, &A, &B);
    S.insert(0);
    LL m = INF, M = -INF;
    for(int i = 1; i <= n; ++i) {
        scanf("%lld", a + i), sum[i] = sum[i-1] + a[i];
        m = min(m, sum[i] - *S.rbegin());
        M = max(M, sum[i] - *S.begin());
        S.insert(sum[i]);
    }
    printf("%lld
", max(A * m, A * M) + B);
    return 0;
}

D.公路收费

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
vector<int> G[1111], D[1111];
int a[1111];

vector<LL> vec;
LL sz[1111];
void dfs(int x, int f) {
    sz[x] = a[x];
    for(int i = 0; i < G[x].size(); ++i) {
        int to = G[x][i], d = D[x][i];
        if(to == f) continue;
        dfs(to, x);
        sz[x] += sz[to];
        vec.push_back(sz[to] * d);
    }
}

int main() {
    int n, k;
    scanf("%d %d", &n, &k);
    for(int i = 1; i <= n; ++i) scanf("%d", a + i);
    for(int i = 1; i < n; ++i) {
        int u, v, w;
        scanf("%d %d %d", &u, &v, &w);
        G[u].push_back(v), D[u].push_back(w);
        G[v].push_back(u), D[v].push_back(w);
    }
    LL ans = 1e18;
    for(int i = 1; i <= n; ++i) {
        vec.clear(), dfs(i, 0);
        sort(vec.begin(), vec.end());
        LL tmp = 0;
        for(int j = 0; j < vec.size() - k; ++j) tmp += vec[j];
        ans = min(ans, tmp);
    }
    printf("%lld
", ans);
    return 0;
}