A - Online Shopping

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <vector>
#include <cmath>
#include <stack>
#include <map>
#include <queue>
#include <set>

using namespace std;
#define PII pair<int,int>
typedef long long LL;
const int N = 1e4 + 10, M = N * 2;
int n, s, k;


int main()
{
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin >> n >> s >> k;
    int sum = 0;
    for (int i = 0; i < n; i ++) 
    {
        int p, q; cin >> p >> q;
        sum += p * q;
    }
    if (sum >= s) cout << sum << endl;
    else cout << sum + k << endl;

    return 0;
}

B - Glass and Mug

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <vector>
#include <cmath>
#include <stack>
#include <map>
#include <queue>
#include <set>

using namespace std;
#define PII pair<int,int>
typedef long long LL;
const int N = 1e5 + 10, M = N * 2;

int main()
{
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    int k, g, m; cin >> k >> g >> m;
    int s1 = g, s2 = m;
    while (k --)
    {
        if (s1 == g) s1 = 0;
        else if (!s2) s2 = m;
        else {
            int c = min(s2, g - s1);
            s2 -= c;
            s1 += c;
        }
    }

    cout << s1 << " " << s2 << endl;

    return 0;
}

C - T-shirts

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <vector>
#include <cmath>
#include <stack>
#include <map>
#include <queue>
#include <set>

using namespace std;
#define PII pair<int,int>
typedef long long LL;
const int N = 1e5 + 10, M = N * 2;
string s;
int n, m;

bool check(int x)
{
    int t1 = x, t2 = m;
    for (int i = 0; i < s.size(); i ++)
    {
        if (s[i] == '1') {
            if (!t2) t1 --;
            else t2 --;
        }
        else if (s[i] == '2') t1 --;
        else if (s[i] == '0') t1 = x, t2 = m;
        if (t1 < 0 || t2 < 0) return false;
    }

    return true;
}

int main()
{
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin >> n >> m >> s;

    int l = 0, r = 1000;
    while (l < r)
    {
        int mid = l + r >> 1;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }

    cout << l << endl;

    return 0;
}

D - Swapping Puzzle

枚举行的所有移动情况和列的所有移动情况，然后计算二者的逆序对即为最少的移动次数。

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <vector>
#include <cmath>
#include <stack>
#include <map>
#include <queue>
#include <set>

using namespace std;
#define PII pair<int,int>
typedef long long LL;
const int N = 6, M = N * 2, INF = 0x7f7f7f7f;
int A[N][N], B[N][N];
int n, m, res = INF;
int p[N], q[N];

bool check()
{
    for (int i = 0; i < n; i ++)
        for (int j = 0; j < m; j ++)
            if (A[p[i]][q[j]] != B[i][j]) return false;
    return true;
}

int main()
{
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin >> n >> m;
    for (int i = 0; i < n; i ++) 
        for (int j = 0; j < m; j ++)
            cin >> A[i][j];
    for (int i = 0; i < n; i ++)
        for (int j = 0; j < m; j ++)
            cin >> B[i][j];

    for (int i = 0; i < n; i ++) p[i] = i;
    for (int i = 0; i < m; i ++) q[i] = i;

    int res = INF;
    do{
        do{
            if (!check()) continue;
            int cnt = 0;
            for (int i = 0; i < n; i ++)
                for (int j = i + 1; j < n; j ++)
                    if (p[i] > p[j]) cnt ++;

            for (int i = 0; i < m; i ++)
                for (int j = i + 1; j < m; j ++)
                    if (q[i] > q[j]) cnt ++;

            res = min(res, cnt);
        }while(next_permutation(q, q + m));
    }while(next_permutation(p, p + n));

    cout << (res == INF ? -1 : res) << endl;

    return 0;
}