CS Academy Seven-segment Display

题目链接：https://csacademy.com/contest/archive/task/seven-segment-display

题目大意：七段显示器能够显示0-9所有数字，不同的数字需要的发光段的个数不同。现在给出K，要求用恰好K个发光段来组成一个最小的数字，数字不允许有前导0，输出最小的数字。

解题思路：可以发现8需要的段最多-7个，而其余的需要的段数都要少于7，因此对于一个能够整除7的K来说，全部输出8一定是最优的。而对于不能整除7的K来说，每次选择一个数字a，使得a所需要的段数大于等于当前的k%7，将a作为当前的最高位的数字，不停重复下去，知道最后k小于7的时候，选择一个对应的最小的即可。需要注意1和6这两个特殊情况。

代码：

int k, mmp[11] = {6, 2, 5, 5, 4, 5, 6, 3, 7, 6};

void solve(){
    if(k == 1){
        puts("-1");
        return;
    }
    else if(k == 6){
        puts("0");
        return;
    }
    bool fir = true;
    while(k > 0){
        int u = k % 7;
        if(u == 0) {
            printf("8");
            k -= 7;
        }
        else{
            for(int i = 0; i <= 9; i++){
                if(i == 0 && fir) continue;
                if(mmp[i] >= u && k - mmp[i] > 0){
                    printf("%d", i);
                    k -= mmp[i];
                    break;
                }
                if(mmp[i] == u && k - mmp[i] == 0){
                    printf("%d", i);
                    k -= mmp[i];
                    break;
                }
            }
        }
        fir = false;
    }
}
int main(){
    scanf("%d", &k);
    solve();
}

题目：

Seven-segment Display

Time limit: 1000 ms
Memory limit: 128 MB

 

A Seven-segment display (SSD), or seven-segment indicator, is a form of electronic display device for displaying decimal numerals.

Below you can see the representation of every decimal digit.

Different digits use a different number of segments in their representation. For example, 00 uses 66 segments, while 11 uses only 22.

You are given a number KK, what is the smallest non-negative integer that uses exactly KK segments in its representation?

Standard input

The first line contains a single integer KK.

Standard output

If there is no solution print -1−1.

Otherwise, print the answer on the first line. The number can be quite large and doesn't necessarily fit in a 64 bit integer.

Constraints and notes

• 1 leq K leq 10^51≤K≤10​5​​ 

Input	Output
7	8
10	22
12	28