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88 lines (78 loc) · 1.81 KB
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// Source : https://oj.leetcode.com/problems/count-and-say/
// Author : Hao Chen
// Date : 2014-07-03
/**********************************************************************************
*
* 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.
*
*
**********************************************************************************/
#include <stdlib.h>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
string vecToStr(vector<int> v) {
stringstream ss;
for (int i=0; i<v.size(); i++) {
ss << v[i];
}
return ss.str();
}
vector<int> getNext(vector<int>& v) {
int cnt=0;
int val=0;
vector<int> ret;
for(int i=0; i<v.size(); i++){
if (i==0){
val = v[i];
cnt = 1;
continue;
}
if (v[i] == val){
cnt++;
}else{
ret.push_back(cnt);
ret.push_back(val);
val = v[i];
cnt = 1;
}
}
if (cnt>0 && val>0){
ret.push_back(cnt);
ret.push_back(val);
}
return ret;
}
string countAndSay(int n) {
if (n<=0) return "";
if (n==1) return "1";
string s;
vector<int> v;
v.push_back(1);
for(int i=2; i<=n; i++){
v = getNext(v);
//s = s + ", " +vecToStr(v);
}
s = vecToStr(v);
return s;
}
int main(int argc, char** argv)
{
int n = 4;
if (argc>1){
n = atoi(argv[1]);
}
cout << countAndSay(n) << endl;
return 0;
}