Dubious Cyrpto CodeForces - 1379B(思维,枚举)

https://codeforces.com/contest/1379/problem/B

题意:

给定l,r,m
要求构造出一组a,b,c,满足:
l<=a,b,c<=r,存在一个正整数n,n*a+b-c=m

数据范围:1<=l,r<=5e^5,1<=m<=1e10

题解:

对等式变换可知:n=(m+c-b)/a; 我们可知c-b的范围是[l-r,r-l];(这里很重要。。。我陷入误区:误认为[0,r-l],一直wrong);

枚举a,要确定n是正整数,那么可知c-b不是a-m%a,就是-m%a,然后我们确定这两个数是不是在[l-r,r-l]内,若在直接输出.

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF=0x3f3f3f3f;
const int maxn=1e5+5;
void io() { ios::sync_with_stdio(0);cin.tie(0);cout.tie(0); }

int main() {
	int test; scanf("%d",&test);
	while(test--) {
		ll m,l,r,a,b,c;
		scanf("%lld%lld%lld",&l,&r,&m);
		ll mx=r-l,mi=l-r;
		for(a=l;a<=r;++a) {
			ll x=m%a;
			ll y=a-x;
			if(y<=mx) {
				b=l;c=l+y;break;
			} else if(-x>=mi) {
				b=r;c=r-x; break;
			}
		}
		printf("%lld %lld %lld\n",a,b,c);
	}
	
	
	return 0;
}

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转载自blog.csdn.net/qq_44132777/article/details/107497255