求助getline()方法在洛谷的使用方式

两段完全相同的逻辑，采用的输入方式不同，导致AC和全WA两个完全不同的结果，请教各位洛谷同学

全WA写法

#include<iostream>
#include<cmath>
#include<cstdio>
#include<algorithm>
#include<string>
#include<set>
#include<unordered_set>
#include<vector>
#include<climits>
#include<limits>
#include<map>
#include<unordered_map>

using namespace std;

int main() {
  string s;
  
  getline(cin, s);
  int n = s.size();
  for (int i = 1; i < n; i++) {
    string str;
    getline(cin, str);
    s.append(str);
  }

  // cout << "s: " << s << "  size: " << s.size() << endl;

  vector<int> v;
  int cnt = 0;
  int i = 0;
  
  if (s[0] == '1') {
    v.push_back(0);
  }

  bool flag = false;
  while (i < s.size()) {
    if (s[i] != '0' && s[i] != '1') {
      i++;
    }

    while (i < s.size() && s[i] == '0') {
      i++;
      cnt++;
      
      flag = true;
    }
    if (flag) {
      v.push_back(cnt);
      flag = false;
      cnt = 0;
    }

    while (i < s.size() && s[i] == '1') {
      i++;
      cnt++;
      flag = true;
    }
    if (flag) {
      v.push_back(cnt);
      flag = false;
      cnt = 0;
    }
  }

  cout << n << ' ';
  for (int i = 0; i < v.size() - 1; i++) {
    cout << v[i] << ' ';
  }
  cout << v[v.size() - 1] << endl;
  return 0;
}

AC写法

#include<iostream>
#include<cmath>
#include<cstdio>
#include<algorithm>
#include<string>
#include<set>
#include<unordered_set>
#include<vector>
#include<climits>
#include<limits>
#include<map>
#include<unordered_map>

using namespace std;

int main() {
  string s;
  
  cin >> s;
  int n = s.size();
  for (int i = 1; i < n; i++) {
    string str;
    cin >> str;
    s.append(str);
  }
  vector<int> v;
  int cnt = 0;
  int i = 0;
  
  if (s[0] == '1') {
    v.push_back(0);
  }

  bool flag = false;
  while (i < s.size()) {
    while (i < s.size() && s[i] == '0') {
      i++;
      cnt++;
      
      flag = true;
    }
    if (flag) {
      v.push_back(cnt);
      flag = false;
      cnt = 0;
    }

    while (i < s.size() && s[i] == '1') {
      i++;
      cnt++;
      flag = true;
    }
    if (flag) {
      v.push_back(cnt);
      flag = false;
      cnt = 0;
    }
  }

  cout << n << " ";
  for (int i = 0; i < v.size() - 1; i++) {
    cout << v[i] << " ";
  }
  cout << v[v.size() - 1] << endl;
  return 0;
}