UVa 1583 Digit Generator

For a positive integer N , the digit-sum of N is defined as the sum of N itself and its digits. When M is the digitsum of N , we call N agenerator of M .

For example, the digit-sum of 245 is 256 (= 245 + 2 + 4 + 5). Therefore, 245 is a generator of 256.

Not surprisingly, some numbers do not have any generators and some numbers have more than one generator. For example, the generators of 216 are 198 and 207.

You are to write a program to find the smallest generator of the given integer.

Input 

Your program is to read from standard input. The input consists of T test cases. The number of test cases T is given in the first line of the input. Each test case takes one line containing an integer N , 1N100, 000 .

Output 

Your program is to write to standard output. Print exactly one line for each test case. The line is to contain a generator of N for each test case. If N has multiple generators, print the smallest. If N does not have any generators, print 0.

The following shows sample input and output for three test cases.

这道题对于每个数字N从1到N-1查找，一直是超时。优化查找方法，也一直是超时。后来没做出来，发现每个数字和它的generator是一一对应的，可以从generator方向来确定其数字。方法是由于最大数字是100000，从1到100000，由generator来确定数字。以后每个数字查数组就可以了。

#include "stdio.h"#include "string.h"#define maxn 100001int generator[maxn];int main(){memset(generator, 0, sizeof(generator));for(int i = 1; i < maxn; i++){int sum = 0, k = i;while(k > 0){sum += k % 10;k = k / 10;}int j = i + sum;if(generator[j] == 0)generator[j] = i;}int n;scanf("%d", &n);for(int i = 1; i <= n; i++){int num;scanf("%d", &num);printf("%d\n", generator[num]);}return 0;}