38. Count and Say
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.
根据规律可以写出后面的:
1. 1 2. 11 3. 21 4. 1211 5. 111221 6. 312211 7. 13112221 8. 1113213211 9. 31131211131221 10. 13211311123113112211
1.用2个串来替换存储记录result,tmp。
2.记录当前值n,获取当前值最大连续长度m。
3.tmp串追加"m",再追加"n"。
代码如下:
class Solution {
public:
string countAndSay(int n) {
if (--n < 0)
return "";
string result = "1";
string tmp; //临时串
int step = 1;//步长
char cur; //当前元素
while (n)
{
cur = result[0];
for (int i = 0; i < result.size(); i++)
{
if ( i+1 < result.size() && result[i] == result[i + 1])
{
step++;
}
else
{
stringstream stepStream;
stepStream << step;
string stepStr = stepStream.str();
tmp.append(1,stepStr[0]);
tmp.append(1,cur);
step = 1;
cur = result[i + 1];
}
}
swap(result, tmp);
tmp = "";
n--;
}
return result;
}
};
2016-08-10 17:24:26
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