湘潭邀请赛——Welcome to XTCPC

Happy Number Accepted : 118   Submit : 303 Time Limit : 1000 MS   Memory Limit : 65536 KB  Problem Description Recently, Mr. Xie learn the concept of happy number. A happy number is a number contain all digit 7 or only 1 digit other than 7. For example, 777 is a happy number because 777 contail all digit 7, 7177 and 87777 both happy number because only 1 digit other than 7. Whereas 887,799 9807,12345, all of them are not happy number. Now Mr. xie want to know for a given integer n, how many number among [1,n] are happy numbers, but counting them one by one is slow, can you help him? Input First line an integer t indicate there are t testcases(1≤t≤100). Then t lines follow, each line an integer n(1≤n≤106, n don't have leading zero). Output Output case number first, then the answer. Sample Input 5 1 7 17 20 30 Sample Output Case 1: 1 Case 2: 7 Case 3: 10 Case 4: 10 Case 5: 11 题意：所谓欢乐数，就是指一个数所有的位数全部都是7，或是只有一个位上的数不是7。计算从1到n欢乐数的个数，需要注意的是若只有1位，则不管是不是7， 都是欢乐数。 开始想找规律，想来想去，还不如暴力简单，毕竟最大只有7位数，那就暴力吧！！暴力万岁！！！！！ #include #include #include #include using namespace std; int main() { int n,i,t,k,m,sum; scanf("%d",&t); for(m=1; m<=t; m++) { sum=9; scanf("%d",&n); if(n<10) { printf("Case %d :%d\n",m,n); continue; } for(k=10; k<=n; k++) { int j=k,p = 0,t1 = 0,w = 0,x; while (j) { x = j%10; j=j/10; t1++; if(x==7) p++; else w++; if(w>=2) break; } if(p==t1||p==t1-1) sum++; } printf("Case %d: %d\n",m,sum); } return 0; }