(java)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.

思路:写一个函数，可以产生下一个sequence的过程.设置一个count=1，while循环中判断连续相同字符的个数。当到不相同时，ans=ans+count+str.charAt(i-1);并将count重新设置为1，循环结束是别忘了ans=ans+count+str.charAt(i-1);然后在主函数里调用n-1次次函数就可以得出结果了.

代码如下(已通过leetcode)

public class Solution {

public String countAndSay(int n) {

if(n==1) return ""+1;

String temp=""+1;

for(int i=2;i<=n;i++) {

temp=getit(temp);

}

return temp;

}

public String getit(String str) {

String ans="";

int count=1;

int i=1;

while(i<str.length()) {

if(str.charAt(i)==str.charAt(i-1)) {

count++;

}

else {

ans=ans+count+str.charAt(i-1);

count=1;

}

i++;

}

ans=ans+count+str.charAt(i-1);

return ans;

}

}