Codeforces 7C Line(拓展欧几里得)
2017-09-26 23:12
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C. Line
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
A line on the plane is described by an equation Ax + By + C = 0. You are to find any point on this line, whose coordinates
are integer numbers from - 5·1018 to 5·1018 inclusive,
or to find out that such points do not exist.
Input
The first line contains three integers A, B and C ( - 2·109 ≤ A, B, C ≤ 2·109)
— corresponding coefficients of the line equation. It is guaranteed that A2 + B2 > 0.
Output
If the required point exists, output its coordinates, otherwise output -1.
Examples
input
output
大意:解二元一次方程,存在输出该解,不存在输出-1
思路:将ax+by+c=0,化为ax+by=-c/gcd(a,b)*gcd(a,b),套拓展欧几里得就可以解出了
上代码:
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
A line on the plane is described by an equation Ax + By + C = 0. You are to find any point on this line, whose coordinates
are integer numbers from - 5·1018 to 5·1018 inclusive,
or to find out that such points do not exist.
Input
The first line contains three integers A, B and C ( - 2·109 ≤ A, B, C ≤ 2·109)
— corresponding coefficients of the line equation. It is guaranteed that A2 + B2 > 0.
Output
If the required point exists, output its coordinates, otherwise output -1.
Examples
input
2 5 3
output
6 -3
大意:解二元一次方程,存在输出该解,不存在输出-1
思路:将ax+by+c=0,化为ax+by=-c/gcd(a,b)*gcd(a,b),套拓展欧几里得就可以解出了
上代码:
/* 对于不完全为0的非负整数a,b,gcd(a, b)表示a, b的最大 公约数,必定存在整数对x,y,满足a*x+b*y==gcd(a, b) 求解不定方程;如a*x+b*y=c; 已知a, b, c的值求x和y的值 a*x+b*y=gcd(a, b)*c/gcd(a, b); 最后转化为 a*x/(c/gcd(a, b))+b*y/(c/gcd(a, b))=gcd(a, b); 最后求出的解x0,y0乘上c/gcd(a, b)就是最终的结果了 x1=x0*c/gcd(a, b); y1=y0*c/gcd(a, b); */ #include<iostream> #include<cmath> #include<cstring> #include<stack> #include<cstdio> #include<string> #include<vector> #include<algorithm> #define M 20010 using namespace std; #define ll long long #define inf 0x3f3f3f3f #define maxn 1000010 //x1 = y2, y1 = x2 - a / b*y2; ll exgcd(ll a, ll b, ll &x, ll &y) { if (b == 0) { x = 1, y = 0; //cout << x << ' ' << y << endl; return a;//最小公约数 } ll g = exgcd(b, a%b, x, y); ll t; t = x, x = y, y = t - (a / b)*y; //cout << x <<' '<< y << endl; return g; } int main() { ll a, b, c, x, y; cin >> a >> b >> c; ll t = exgcd(a, b, x, y); if (c%t == 0)//点是否为整数 printf("%lld %lld\n", -x*c / t, -y*c / t); else printf("-1\n"); return 0; }
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