SGU107 - 987654321 problem
107. 987654321 problem time limit per test: 0.5 sec.
For given number N you must output amount of N-digit numbers, such, that last digits of their square is equal to 987654321.
Input Input contains integer number N (1<=N<=106)
Output Write answer to the output.
Sample Input 8
Sample Output 0
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题解:用枚举显然超时。只能用观察法了。小于八位的情况数为0,九位有8种情况,当N>9时,九位以上的数字对于后九位都是没有影响的,所以最高位有9种取法,其余大于九位的都是10种取法。然后运用乘法原理得出最终答案。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include<stdio.h> 2 int main(void) 3 { 4 int n,i; 5 scanf("%d",&n); 6 if(n<=8) printf("0\n"); 7 else 8 if(n==9) printf("8\n"); 9 else 10 { 11 printf("72"); 12 for(i=11;i<=n;i++) 13 printf("0"); 14 printf("\n"); 15 } 16 return 0; 17 }