题解 P1626 【象棋比赛】

zqiceberg · 2019-10-23 14:05:39 · 题解

第一种算法 sort()

//sort()的参数 ，n个数
//如果下标从0到n，sort(q, q + n)
//如果下标从1到n，sort(q + 1, q + 1 + n)
//如果下标从2到n，sort(q + 2, q + 2 + n -1) 

#include <iostream>
#include <algorithm>
#include <fstream>

using namespace std;

const int N = 100010;

int q[N], cha[N];
int ans;

int main()
{
//  freopen("xiangqi.in", "r", stdin);
    int n, k;
    cin >> n >> k;

    for (int i = 1; i <= n; i++) scanf("%d", &q[i]);

    sort(q + 1, q + n + 1);

//  for (int i = 1; i <= n; i++) printf("%d ", q[i]);
//  puts("");

    for (int i = 2, k = 2; i <= n; i++, k++)
        cha[k] = q[i] - q[i - 1];

    sort(cha + 2, cha + n + 1);

//  for (int i = 2; i <= n; i++) printf("%d ", cha[i]);
//  puts("");

    for (int i = 2; i <= 2 + k - 1; i++) 
        ans += cha[i];

    cout << ans << endl;

    return 0;
}

第二种算法 merge_sort()

#include <iostream>
#include <cstdio>
#include <fstream>

using namespace std;

const int N = 100010;

int q[N], tmp[N], cha[N];
int ans;

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

int main()
{
//  freopen("xiangqi.in", "r", stdin);
    int n, k;
    cin >> n >> k;

    for (int i = 1; i <= n; i++) scanf("%d", &q[i]);
    merge_sort(q, 1, n);

    for (int i = 2; i <= n; i++) cha[i] = q[i] - q[i - 1];
    merge_sort(cha, 2, n);

//  for (int i = 2; i <= n; i++) printf("%d ", cha[i]);
    for (int i = 2; i <= 2 + (k - 1); i++) ans += cha[i];

    cout << ans << endl;

    return 0;
}