Codeforces Round #427 (Div. 2)

题目链接：http://codeforces.com/contest/835/problem/B

题意：给定一个数k和一个数字串n。问你最少改几个数字才能满足所有数字的和不小于k。

思路：考虑贪心，每次肯定把最小的数字改成'9' 会使得所有数字的和最大。

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<time.h>
#include<cmath>
#include<set>
#include<map>
using namespace std;
typedef long long int LL;
const int MAXN = 100000 + 24;
const int INF = 1e9;
const int mod = 1e9 + 7;
char n[MAXN];
int main(){
#ifdef kirito
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif
    int k;
    while (~scanf("%d", &k)){
        scanf("%s", n);
        int sum = 0,len=strlen(n),res=0;
        for (int i = 0; i < len; i++){
            sum += (n[i] - '0');
        }
        sort(n, n + len);
        for (int i = 0; i < len&&sum<k; i++,res++){
            sum = (sum - (n[i] - '0') + 9);
        }
        printf("%d
", res);
    }
    return 0;
}