题解 | #游游的整数切割#

#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll>PII;
const int N = 5e5 + 10;
const int MOD = 998244353;
const int INF = 0X3F3F3F3F;
const int dx[] = {-1, 1, 0, 0, -1, -1, +1, +1};
const int dy[] = {0, 0, -1, 1, -1, +1, -1, +1};
const int M = 1e6 + 10;

int main()
{
    string s;
	cin >> s;
	ll n = s.size();
	s = ' ' + s;
    //直接看末尾即可
	int o = (int)(s[n] - '0');
	if(o & 1) o = 1;
	else o = 2;
	int cnt = 0;
	for(int i = 1; i <= n - 1; i ++)
	{
		if(o == 1 && ((int)(s[i] - '0')) & 1) cnt ++;
		if(o == 2 && ((int)(s[i] - '0')) % 2 == 0) cnt ++;
	}
	cout << cnt << endl;
}