一、题目
Look-and-say sequence is a sequence of integers as the following:
D, D1, D111, D113, D11231, D112213111, ...
where D
is in [0, 9] except 1. The (n+1)st number is a kind of description of the nth number. For example, the 2nd number means that there is one D
in the 1st number, and hence it is D1
; the 2nd number consists of one D
(corresponding to D1
) and one 1 (corresponding to 11), therefore the 3rd number is D111
; or since the 4th number is D113
, it consists of one D
, two 1's, and one 3, so the next number must be D11231
. This definition works for D
= 1 as well. Now you are supposed to calculate the Nth number in a look-and-say sequence of a given digit D
.
Input Specification:
Each input file contains one test case, which gives D
(in [0, 9]) and a positive integer N (≤ 40), separated by a space.
Output Specification:
Print in a line the Nth number in a look-and-say sequence of D
.
Sample Input:
1 8
Sample Output:
1123123111
二、题目大意
给定数字和规则,求序列。
三、考点
找规律
四、注意
1、循环的时候注意++和截止条件。
五、代码
#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main() {
//read
string d;
int n;
cin >> d >> n;
vector<string> v(n);
v[0] = d;
for (int i = 1; i < n; ++i) {
for (int j = 0; j < v[i - 1].size(); ) {
char c = v[i - 1][j];
int num = 0;
while (j < v[i - 1].size() && c == v[i - 1][j]) {
j++;
num++;
}
v[i] += c;
v[i] += to_string(num);
}
}
cout << v[n - 1];
system("pause");
return 0;
}