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1 /*
2 数学：这题一直WA在13组上，看了数据才知道是计算cost时超long long了
3 另外不足一个区间的直接计算个数就可以了
4 */
5 #include <cstdio>
6 #include <cmath>
7 #include <iostream>
8 #include <algorithm>
9 #include <cstring>
10 using namespace std;
11
12 typedef unsigned long long ull;
13 int get_len(ull x)
14 {
15 int ret = 0;
16 while (x) {
17 x /= 10; ret++;
18 }
19 return ret;
20 }
21
22
23 int main(void) //Codeforces Round #219 (Div. 2) B. Making Sequences is Fun
24 {
25 //freopen ("B.in", "r", stdin);
26
27 ull w, m, k;
28 while (cin >> w >> m >> k) {
29 int len = get_len (m); ull mx = 0;
30 for (int i=1; i<=len; ++i) {
31 mx = mx * 10 + 9;
32 }
33
34 ull ans = 0; ull cost = (mx - m + 1) * k * len;
35 while (cost <= w) {
36 w -= cost; ans += (mx - m + 1);
37 len++; m = mx + 1; mx = mx * 10 + 9;
38 cost = (mx - m + 1) * k * len;
39 }
40
41 ans += w / (len * k);
42 cout << ans << endl;
43 }
44
45 return 0;
46 }
1 #include <cstdio> 2 #include <cmath> 3 #include <iostream> 4 #include <algorithm> 5 #include <cstring> 6 using namespace std; 7 8 typedef long long ll; 9 int get_len(ll x) 10 { 11 int ret = 0; 12 while (x) { 13 x /= 10; ret++; 14 } 15 return ret; 16 } 17 18 19 int main(void) //Codeforces Round #219 (Div. 2) B. Making Sequences is Fun 20 { 21 //freopen ("B.in", "r", stdin); 22 23 ll w, m, k; 24 while (scanf ("%I64d%I64d%I64d", &w, &m, &k) == 3) { 25 int len = get_len (m); ll mx = 0; 26 for (int i=1; i<=len; ++i) { 27 mx = mx * 10 + 9; 28 } 29 30 ll ans = 0, now = 0, tot = 0; 31 while (true) { 32 now = mx - m + 1; tot = w / (k * len); 33 if (now < tot) { 34 ans += now; w -= now * k * len; 35 m = mx + 1; mx = mx * 10 + 9; len++; 36 } 37 else { 38 ans += tot; break; 39 } 40 } 41 42 printf ("%I64d\n", ans); 43 } 44 45 return 0; 46 }
数学 Codeforces Round #219 (Div. 2) B. Making Sequences is Fun
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原文地址：http://www.cnblogs.com/Running-Time/p/4658514.html
