A - Transformation: from A to B

CodeForces - 727A

Vasily has a number a, which he wants to turn into a number b. For this purpose, he can do two types of operations:

multiply the current number by 2 (that is, replace the number x by 2·x);
append the digit 1 to the right of current number (that is, replace the number x by 10·x + 1).
You need to help Vasily to transform the number a into the number b using only the operations described above, or find that it is impossible.

Note that in this task you are not required to minimize the number of operations. It suffices to find any way to transform a into b.

Input
The first line contains two positive integers a and b (1 ≤ a < b ≤ 109) — the number which Vasily has and the number he wants to have.

Output
If there is no way to get b from a, print "NO" (without quotes).

Otherwise print three lines. On the first line print "YES" (without quotes). The second line should contain single integer k — the length of the transformation sequence. On the third line print the sequence of transformations x1, x2, ..., xk, where:

x1 should be equal to a,
xk should be equal to b,
xi should be obtained from xi - 1 using any of two described operations (1 < i ≤ k).
If there are multiple answers, print any of them.

Example
Input
2 162
Output
YES
5
2 4 8 81 162
Input
4 42
Output
NO
Input
100 40021
Output
YES
5
100 200 2001 4002 40021

题意：你有一个起始数，你可以乘2或者乘10再加1这两种操作方式，问怎么操作能够变成目标数

解法：倒着推即可

代码：

#include<iostream>
#include<stdio.h>
#include<math.h>
using namespace std;
int main()
{
    double a,b,n,x,y,v,t,ans=999999999;
    scanf("%lf%lf%lf",&a,&b,&n);
    for(int i=0;i<n;i++){
        cin>>x>>y>>v;
        t=sqrt((x-a)*(x-a)+(y-b)*(y-b))/v;
        ans=min(ans,t);
    }
    printf("%.20lf",ans);
    return 0;
}