AtCoder Beginner Contest 135

AtCoder Beginner Contest 135

A - Harmony

#include <bits/stdc++.h>

using namespace std;

int main () {
    int a, b;
    cin >> a >> b;
    if (a == b) cout << 0;
    else {
        int ans = (a + b) / 2;
        if (a + b & 1)  cout << "IMPOSSIBLE";
        else if (ans < min (a, b) || ans > max (a, b))  cout << "IMPOSSIBLE";
        else    cout << ans;
    }

}

B - 0 or 1 Swap

#include <bits/stdc++.h>

using namespace std;
const int N = 55;
int a[N], n, cnt;

int main () {
    cin >> n;
    for (int i = 1; i <= n; i++)    cin >> a[i];
    for (int i = 1; i <= n; i++) {
        if (i != a[i])  cnt ++;
    }
    if (cnt == 2 || !cnt)    cout << "YES";
    else    cout << "NO";
}

C - City Savers

#include <bits/stdc++.h>
#define int long long

using namespace std;
const int N = 1e5 + 5;
int a[N], n, ans;

signed main () {
    cin >> n;
    for (int i = 1; i <= n + 1; i++)    cin >> a[i];
    for (int i = 1; i <= n; i++) {
        int x;  cin >> x;
        ans += min (x, a[i] + a[i+1]);
        a[i+1] -= min (a[i+1], max(0ll, x - a[i]));
    }
    cout << ans;
}

D - Digits Parade

#include <bits/stdc++.h>
#define int long long

using namespace std;
const int N = 1e5 + 5, mod = 1e9 + 7;
int f[N][13], n;

signed main () {
    string s;
    cin >> s;
    n = s.size ();
    s = ' ' + s;
    f[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        if (s[i] != '?') {
            int x = s[i] - '0';
            for (int j = 0; j < 13; j++) {
                (f[i][(j * 10 + x) % 13] += f[i-1][j]) %= mod;
            }
        }
        else {
            for(int k = 0; k < 10; k++) {
                for (int j = 0; j < 13; j++) {
                    (f[i][(j * 10 + k) % 13] += f[i-1][j]) %= mod;
                }
            }
        }
    }
    cout << f[n][5] << endl;
}

E - Golf

难想

#include <bits/stdc++.h>

using namespace std;

int main () {
    int k, n, fx, fy;
    cin >> k >> fx >> fy;
    int signx = 1, signy = 1;
    if (fx < 0)     signx = -1;
    if (fy < 0)     signy = -1; //转换到第一象限做
    fx = abs (fx), fy = abs (fy);
    if ((fx + fy & 1) && k % 2 == 0) {
        cout << "-1\n";
        return 0;
    }
    if (k == fx + fy)     n = 1; //一步到达
    else {
        n = max(2, (fx + fy + k - 1) / k);
        while ((n * k - fx - fy) & 1)   n ++;
    }

    cout << n << endl;
    int neg = (n * k - fx - fy) / 2, pos = (n * k + fx + fy) / 2;
    int x = 0, y = 0;
    for (int i = 0; i < n; i++) {
        if (neg > 0) { //先反向移动
            if (neg >= k) {
                if (fx - x <= fy - y)   x -= k;
                else    y -= k;
                neg -= k;
            }
            else {
                if (fx - x <= fy - y)   x -= neg, y += k - neg;
                else    y -= neg, x += k - neg;
                neg = 0;
            }
        }
        else {
            if (x < fx) {
                if (fx - x >= k)    x += k;
                else    y += k - (fx - x), x = fx;
            }
            else    y += k;
        }
        cout << x * signx << ' ' << y * signy << endl;
    }    
}

//fx + fy >= nk && (nk - (fx+fy)) % 2 == 0

F - Strings of Eternity