Chinese remainder theorem again(hdu 1788)两种解法:线性同余方程或者简单的最小公倍数
2016-08-09 09:46
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大概题意:有个最小的N,使得N(mod M[i])=M[i]-a;这里1<=i<=k,1<k<10.就是求出最小的N就行,这里我提供两种思路:
1:线性同余方程的解法:
第二种解法的分析:
N%M[i]=M[i]-a;
N%M[i]+a=M[i];
(N+a)%M[[i]=0;
就代表N+a就是M[i]的最小公倍数,其中i就是1到k;
下边请见代码实现:
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
using namespace std;
typedef long long LL;
int n;
int times;
const int MAXN = 1010;
LL A[MAXN], r[MAXN];
LL lcm;
LL gcd(LL a, LL b)
{
return b == 0? a : gcd(b, a%b);
}
int main()
{
int k,a;
while(~scanf("%d%d",&n,&k),n||k)
{
LL temp=1;
for(int i=0;i<n;i++)
{
scanf("%d",&a);
temp=(temp/gcd(a,temp))*a;
}
printf("%lld\n",temp-k);
}
}
1:线性同余方程的解法:
#include <iostream> #include <cstdlib> #include <cstdio> #include <cstring> using namespace std; typedef long long LL; int n; int times; const int MAXN = 1010; LL A[MAXN], r[MAXN]; LL lcm; LL gcd(LL a, LL b) { return b == 0? a : gcd(b, a%b); } void ex_gcd(LL a, LL b, LL &d, LL &x, LL &y) { if(!b) { d = a; x = 1; y = 0;} else { ex_gcd(b, a%b, d, y, x); y -= x*(a/b);} } void read_case() { } void solve() { int p; while(~scanf("%d%d", &n,&p),n||p) { lcm = 1; for(int i = 1; i <= n; i++) { scanf("%lld", &A[i]); lcm = lcm / gcd(lcm, A[i]) * A[i]; r[i]=A[i]-p; } // for(int i = 1; i <= n; i++) scanf("%lld", &r[i]); LL a, b, c, d, x, y; for(int i = 2; i <= n; i++) { a = A[1], b = A[i], c = r[i]-r[1]; ex_gcd(a, b, d, x, y); if(c % d) { printf("-1\n"); return ;} LL b1 = b / d; x *= c / d; x = (x%b1 + b1) % b1; r[1] = A[1]*x + r[1]; A[1] = A[1]*(A[i] / d); } if(r[1] == 0) printf("%lld\n", lcm); else printf("%lld\n", r[1]); } } int main() { int T; times = 0; solve(); return 0; }
第二种解法的分析:
N%M[i]=M[i]-a;
N%M[i]+a=M[i];
(N+a)%M[[i]=0;
就代表N+a就是M[i]的最小公倍数,其中i就是1到k;
下边请见代码实现:
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
using namespace std;
typedef long long LL;
int n;
int times;
const int MAXN = 1010;
LL A[MAXN], r[MAXN];
LL lcm;
LL gcd(LL a, LL b)
{
return b == 0? a : gcd(b, a%b);
}
int main()
{
int k,a;
while(~scanf("%d%d",&n,&k),n||k)
{
LL temp=1;
for(int i=0;i<n;i++)
{
scanf("%d",&a);
temp=(temp/gcd(a,temp))*a;
}
printf("%lld\n",temp-k);
}
}
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