【CodeForces】388B Fox and Minimal path

传送门

题目描述

Fox Ciel wants to write a task for a programming contest. The task is: "You are given a simple undirected graph with n vertexes. Each its edge has unit length. You should calculate the number of shortest paths between vertex 1 and vertex 2."

Same with some writers, she wants to make an example with some certain output: for example, her birthday or the number of her boyfriend. Can you help her to make a test case with answer equal exactly to k?

解题思路

代码

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 bool map[1005][1005];
 7 inline void add(int f,int t){
 8     map[t][f]=map[f][t]=1;
 9 }
10 inline void ini(){
11     add(1,3),add(1,4),add(2,100);
12     for(register int i=3;i<60;i+=2)add(i,i+2),add(i,i+3),add(i+1,i+2),add(i+1,i+3);
13     for(register int i=63;i<100;i++)add(i,i+1);
14 }
15 int main(){
16     ini();
17     int k;
18     cin>>k;
19     for(register int i=30;i;i--){
20         if(k>=(1<<i)){
21             k-=(1<<i);
22             add(2*i+1,63+i),add(2*i+2,63+i);
23         }
24     }
25     if(k)add(1,63);
26     cout<<100<<endl;
27     for(register int i=1;i<=100;i++){
28         for(register int j=1;j<=100;j++){
29             if(map[i][j])putchar('Y');
30             else putchar('N');
31         }
32         putchar('\n');
33     }
34     return 0;
35 }