You are given three integers aa, bb and xx. Your task is to construct a binary string ss of length n=a+bn=a+b such that there are exactly aa zeroes, exactly bb ones and exactly xx indices ii (where 1≤i<n1≤i<n) such that si≠si+1si≠si+1. It is guaranteed that the answer always exists.
For example, for the string "01010" there are four indices ii such that 1≤i<n1≤i<n and si≠si+1si≠si+1 (i=1,2,3,4i=1,2,3,4). For the string "111001" there are two such indices ii (i=3,5i=3,5).
Recall that binary string is a non-empty sequence of characters where each character is either 0 or 1.
The first line of the input contains three integers aa, bb and xx (1≤a,b≤100,1≤x<a+b)1≤a,b≤100,1≤x<a+b).
Print only one string ss, where ss is any binary string satisfying conditions described above. It is guaranteed that the answer always exists.
2 2 1
1100
3 3 3
101100
5 3 6
01010100
All possible answers for the first example:
- 1100;
- 0011.
All possible answers for the second example:
- 110100;
- 101100;
- 110010;
- 100110;
- 011001;
- 001101;
- 010011;
- 001011.
题意:给出a,b,x,构造一个01串,有a个0,b个1。这个01串刚好有x个 ai 使得ai!=ai+1。
思路:对于x,我们很容易就可以想到先输出x/2对0和1(n对0和1交错出现可以提供2*n-1个符合题意的ai),然后将剩余的0和剩余的1连续输出(提供1个符合条件的ai,这样就刚好是x个符合条件的ai了,需要注意的是,我们要优先将个数多的放在前面,例如,有10个1,5个0的话,我们先输出x/2个“10”,否则,输出x/2个“01”)。
#include "iostream"
using namespace std;
int main()
{
int a,b,x,n;
char u,v;
cin>>a>>b>>x;
n=a+b;
if(a>b) u='0',v='1';
else {u='1',v='0';swap(a,b);}
for(int i=0;i<x/2;i++) {cout<<u<<v;a--,b--;}
if(x%2==0){
while(b--) cout<<v;
while(a--) cout<<u;
}
else{
while(a--) cout<<u;
while(b--) cout<<v;
}
return 0;
}