LeetCode: Count and Say 题解

The count-and-say sequence is the sequence of integers beginning as follows:

1, 11, 21, 1211, 111221, ...

1

is read off as

"one 1"

or

11

.

11

is read off as

"two 1s"

or

21

.

21

is read off as

"one 2

, then

one 1"

or

1211

.

Given an integer n, generate the nth sequence.

Note: The sequence of integers will be represented as a string.

本题的难点在于理解题目的意思。

最好的理解就是给出 111221之后的一个sample： 312211

如何理解呢？ 将111221 拆成后面的表达式即可： 111， 22， 1 其中有 3个one ， 2个two， 1个one ，读起来就是： 312211

 class Solution {
public:
string countAndSay(int n) {
string a="1";
if(n==1) return a;
for(int i=2;i<=n;i++)
{
string b;
char current = a[0];
int j=1,count=1;
for(j=1;j<a.size();j++)
{
if(a[j]==current)
{
count++;
}
else
{
char c = count +'0';
b+=c;
b+=current;
current = a[j];
count=1;
}
}
char c = count+'0';
b+=c;
b+=current;
a= b;
}
return a;
}
};

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