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Sequence

Today, Soda has learned a sequence whose n-th(n≥1) item is 3n(n?1)+1. Now he wants to know if an integer m can be represented as the sum of some items of that sequence. If possible, what are the minimum items needed?

For example, 22=19+1+1+1=7+7+7+1.

There are multiple test cases. The first line of input contains an integerT(1≤T≤104), indicating the number of test cases. For each test case:

There‘s a line containing an integer m(1≤m≤109).

For each test case, output ?1 if m cannot be represented as the sum of some items of that sequence, otherwise output the minimum items needed.

10
1
2
3
4
5
6
7
8
22
10

1
2
3
4
5
6
1
2
4
4

 题意，给出一个数列3n(n?1)+1，再给一个任意一个数m，要求最少能用多少个数列中的数之和为m

#define N 205
#define M 100005
#define maxn 205
#define MOD 1000000000
int n,glen,len,pn,m,pri[M];
set<int> myset;
set<int>::iterator it;
bool solve1(int mm){
    return myset.count(mm);
}
bool solve2(int mm){
    for(int i = 0,j = pn -1;i< pn && pri[i] <= mm;i++){
        while(j>= 0 && pri[i] + pri[j] > mm)j--;
        if(j>=0 && pri[i] + pri[j] == mm) return true;
    }
    return false;
}
int main()
{
    pn = 0;
    for(int i = 1;i< M -1 ;i++){
        int t = 3 * i * (i-1) + 1;
        if(t <= MOD){
            pri[pn++] = t;
            myset.insert(t);
        }
        else break;
    }
    while(S(n)!=EOF)
    {
        while(n--){
            S(m);
            if(m%6 == 1){
                if(solve1(m))
                    printf("1\n");
                else
                    printf("7\n");
                continue;
            }
            else if(m%6 == 2)
            {
                if(solve2(m))
                    printf("2\n");
                else
                    printf("8\n");
                continue;
            }
            else
                printf("%d\n",(m - 1)%6 + 1);
        }
    }
    return 0;
}

hdu 5312 三角形数 二分查找

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原文地址：http://blog.csdn.net/mengzhengnan/article/details/47084661