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活动打卡代码 AcWing 790. 数的三次方根

#include <iostream>
#include <cstdio>

using namespace std;

int main()
{
    double x;
    cin >> x;

    double l = -10000, r = 10000;
    while (r - l > 1e-8)
    {
        double mid = (l + r) / 2;
        if (mid * mid * mid >= x) r = mid;
        else l = mid;
    }
    printf("%.6lf", l);

    return 0;
}


活动打卡代码 AcWing 789. 数的范围

#include <iostream>
#include <cstdio>

using namespace std;

const int N = 100010;

int n, m;
int q[N];

int main()
{
    cin >> n >> m;
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    while (m -- )
    {
        int x;
        cin >> x;
        int l = 0, r = n - 1;
        while (l < r)
        {
            int mid = l + r >> 1;
            if (q[mid] >= x) r = mid;
            else l = mid + 1;
        }
        if (q[l] != x) cout << "-1 -1" << endl;
        else
        {
            cout << l << " ";
            int l = 0, r = n - 1;
            while (l < r)
            {
                int mid = l + r + 1 >> 1;
                if (q[mid] <= x) l = mid;
                else r = mid - 1;
            }
            cout << l << endl;
        }
    }

    return 0;
}


活动打卡代码 AcWing 788. 逆序对的数量

#include <iostream>

using namespace std;

typedef long long LL;

const int N = 1e5 + 10;

int n;
int q[N], tmp[N];

LL merge_sort(int l, int r)
{
    if (l >= r) return 0;

    int mid = (l + r) >> 1;
    LL res = merge_sort(l, mid) + merge_sort(mid + 1, r);

    int k = 0, i = l, j = mid + 1;
    while (i <= mid && j <= r)
    {
        if (q[i] <= q[j]) tmp[k ++ ] = q[i ++ ];
        else
        {
            tmp[k ++ ] = q[j ++ ];
            res += mid - i + 1;
        }
    }

    while (i <= mid) tmp[k ++ ] = q[i ++ ];
    while (j <= r) tmp[k ++ ] = q[j ++ ];

    for (i = l, j = 0; i <= r; i ++, j ++ ) q[i] = tmp[j];

    return res;
}

int main()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    printf("%lld", merge_sort(0, n - 1));

    return 0;
}


新鲜事 原文

AcWing《语法基础课》拼团优惠! https://www.acwing.com/activity/content/introduction/21/group_buy/137769/


活动打卡代码 AcWing 787. 归并排序

#include <iostream>

using namespace std;

const int N = 1e6 + 10;

int n;
int q[N], tmp[N];

void merge_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int mid = (l + r) >> 1;
    merge_sort(q, l, mid);
    merge_sort(q, mid + 1, r);

    int k = 0, i = l, j = mid + 1;
    while (i <= mid && j <= r)
    {
        if (q[i] <= q[j]) tmp[k ++ ] = q[i ++ ];
        else tmp[k ++ ] = q[j ++ ];
    }

    while (i <= mid) tmp[k ++ ] = q[i ++ ];
    while (j <= r) tmp[k ++ ] = q[j ++ ];

    for (i = l, j = 0; i <= r; i ++, j ++ ) q[i] = tmp[j];
}

int main()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    merge_sort(q, 0, n - 1);

    for (int i = 0; i < n; i ++ ) printf("%d ", q[i]);

    return 0;
}


活动打卡代码 AcWing 786. 第k个数

#include <iostream>

using namespace std;

const int N = 1e6 + 10;

int n, k;
int q[N];

void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int i = l - 1, j = r + 1, x = q[(l + r) >> 1];
    while (i < j)
    {
        do i ++ ; while (q[i] < x);
        do j -- ; while (q[j] > x);
        if (i < j) swap(q[i], q[j]);
    }

    quick_sort(q, l, j);
    quick_sort(q, j + 1, r);
}

int main()
{
    scanf("%d%d", &n, &k);
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    quick_sort(q, 0, n - 1);

    printf("%d", q[k - 1]);

    return 0;
}


活动打卡代码 AcWing 785. 快速排序

#include <iostream>

using namespace std;

const int N = 1e6 + 10;

int n;
int q[N];

void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int i = l - 1, j = r + 1, x = q[(l + r) >> 1];
    while (i < j)
    {
        do i ++ ; while (q[i] < x);
        do j -- ; while (q[j] > x);
        if (i < j) swap(q[i], q[j]);
    }

    quick_sort(q, l, j);
    quick_sort(q, j + 1, r);
}

int main()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    quick_sort(q, 0, n - 1);

    for (int i = 0; i < n; i ++ ) printf("%d ", q[i]);

    return 0;
}


新鲜事 原文

两门课都差一位,有朋友要一起拼吗 AcWing《算法提高课》拼团优惠! https://www.acwing.com/activity/content/introduction/16/group_buy/134690/ AcWing《算法基础课》拼团优惠! https://www.acwing.com/activity/content/introduction/11/group_buy/134782/