http://acm.hdu.edu.cn/showproblem.php?pid=3555
题意，1-n, 有多少个数含有49
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdlib> 5 #include <cstdio> 6 #include <vector> 7 #include <ctime> 8 #include <queue> 9 #include <list> 10 #include <set> 11 #include <map> 12 using namespace std; 13 #define INF 0x3f3f3f3f 14 typedef long long LL; 15 16 LL dp[25][5]; 17 // dp[1][0] = 10;//没有49 18 // dp[1][1] = 1;//9 19 // dp[1][2] = 0;//有49 20 void find() 21 { 22 memset(dp, 0, sizeof(dp)); 23 dp[0][0] = 1; 24 for(int i = 1; i <= 20; i++) 25 { 26 dp[i][0] = (LL)dp[i - 1][0] * 10 - dp[i - 1][1]; 27 dp[i][1] = dp[i - 1][0]; 28 dp[i][2] = (LL)dp[i - 1][2] * 10 + dp[i - 1][1]; 29 } 30 } 31 32 void solve(LL n) 33 { 34 int len = 0; 35 int bit[25]; 36 while(n) 37 { 38 bit[++len] = n % 10; 39 n /= 10; 40 } 41 bit[len + 1] = 0; 42 LL ans = 0; 43 int flag = 0; 44 for(int i = len; i > 0; i--) 45 { 46 ans += (LL)dp[i - 1][2] * bit[i]; 47 if(flag) 48 ans += (LL)dp[i - 1][0] * bit[i]; 49 if(!flag && bit[i] > 4) 50 ans += dp[i - 1][1]; 51 if(bit[i + 1] == 4 && bit[i] == 9) 52 flag = 1; 53 } 54 printf("%I64d ", ans); 55 } 56 int main() 57 { 58 int t; 59 LL n; 60 scanf("%d", &t); 61 find(); 62 while(t--) 63 { 64 scanf("%I64d", &n); 65 solve(n + 1); 66 } 67 return 0; 68 }