Codeforces 835 B The number on the board

题目地址
题意：给你个字符串，把每个字符的和求出来，然后修改最少的字符数使它的和大于等于n
思路：记录每个字符的个数，并且求出当前和与n的差值，然后从最小的字符把它改成9，然后判断下是不是到了n就好了

#include <iostream>#include <cstring>#include <string>#include <queue>#include <vector>#include <map>#include <set>#include <stack>#include <cmath>#include <cstdio>#include <algorithm>#define N 50010#define M 200010#define K 1000010#define LL __int64#define inf 0x3f3f3f3f#define lson l,mid,ans<<1#define rson mid+1,r,ans<<1|1using namespace std;const LL mod = 1e9 + 7;const double eps = 1e-9;vector<int>num[10];int main() {    cin.sync_with_stdio(false);    string str;    LL n, sum;    while (cin >> n) {        cin >> str;        sum = 0;        for (int i = 0; i < str.length(); i++) {            sum += (str[i] - '0');            num[str[i] - '0'].push_back(i);        }        if (sum >= n) {            cout << "0" << endl;        }        else {            LL cnt = 0;            sum = n - sum;            for (int i = 0; i < 10; i++) {                int len = num[i].size();                LL ans = len * (9 - i);                if (ans >= sum) {                    cnt += sum / (9 - i);                    if (sum % (9 - i)) {                        cnt++;                    }                    break;                }                else {                    cnt += len;                    sum -= ans;                }            }            cout << cnt << endl;        }    }    return 0;}