cf1556A. A Variety of Operations

Posted 2021-09-17 Jozky86

cf1556A. A Variety of Operations

题意：

有两个数a，b一开始都是0，现在有三种操作：

1. 给a和b都加k
2. a加k，b减k
3. a减k，b加k
   问从a=0，b=0到a=c，b=d最少需要几步？

题解：

k=(c+d)/2
我们可以先用第一种操作将0，0都加到k,k.然后一个减，一个加，实现到c，d，这样需要两步
如果c和d的差为奇数，则无法通过操作实现

代码：

// Problem: A. A Variety of Operations
// Contest: Codeforces - Deltix Round, Summer 2021 (open for everyone, rated, Div. 1 + Div. 2)
// URL: https://codeforces.com/contest/1556/problem/A
// Memory Limit: 256 MB
// Time Limit: 1000 ms
// Data:2021-08-31 23:35:41
// By Jozky

#include <bits/stdc++.h>
#include <unordered_map>
#define debug(a, b) printf("%s = %d\\n", a, b);
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> PII;
clock_t startTime, endTime;
//Fe~Jozky
const ll INF_ll= 1e18;
const int INF_int= 0x3f3f3f3f;
void read(){};
template <typename _Tp, typename... _Tps> void read(_Tp& x, _Tps&... Ar)
{
    x= 0;
    char c= getchar();
    bool flag= 0;
    while (c < '0' || c > '9')
        flag|= (c == '-'), c= getchar();
    while (c >= '0' && c <= '9')
        x= (x << 3) + (x << 1) + (c ^ 48), c= getchar();
    if (flag)
        x= -x;
    read(Ar...);
}
template <typename T> inline void write(T x)
{
    if (x < 0) {
        x= ~(x - 1);
        putchar('-');
    }
    if (x > 9)
        write(x / 10);
    putchar(x % 10 + '0');
}
void rd_test()
{
#ifdef LOCAL
    startTime= clock();
    freopen("in.txt", "r", stdin);
#endif
}
void Time_test()
{
#ifdef LOCAL
    endTime= clock();
    printf("\\nRun Time:%lfs\\n", (double)(endTime - startTime) / CLOCKS_PER_SEC);
#endif
}
int main()
{
    //rd_test();
    int t;
    read(t);
    while (t--) {
        int c, d;
        read(c, d);
        if (c > d)
            swap(c, d);
        int w= d - c;
        if (d == 0 && c == 0)
            printf("0\\n");
        else if (w == 0)
            printf("1\\n");
        else {
            if (w % 2 == 1)
                printf("-1\\n");
            else
                printf("2\\n");
        }
    }
    return 0;
    //Time_test();
}