UVA - 10125 Sumsets

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题目：

Problem C - Sumsets

Given S, a set of integers, find the largest d such that a + b + c = d where a, b, c, and d are distinct elements of S.

Input

Several S, each consisting of a line containing an integer 1 <= n <= 1000 indicating the number of elements in S, followed by the elements of S, one per line. Each element of S is a distinct integer between -536870912 and +536870911 inclusive. The last line of input contains 0.

Output

For each S, a single line containing d, or a single line containing "no solution".

Sample Input

52 3 5 7 1252 16 64 256 10240

Output for Sample Input

12no solution

#include <cstdlib>  #include <cstdio>  #include <cstring>  #include <string>  #include <algorithm>  using namespace std;    const int MAXN = 10000003;  const int MAXSIZE = 1030;    int n;  int rear;    struct node  {      int i, j;  }st[MAXSIZE*MAXSIZE];    int first[MAXN], next[MAXSIZE*MAXSIZE];  int A[MAXSIZE];  int sum[MAXSIZE*MAXSIZE];    void init()  {      rear = 0;      memset(first, -1, sizeof(first));  }    int hash(int s)  {      int h = s & 0x7fffffff;      return h % MAXN;  }    void insert(int s)  {      int h = hash(sum[s]);      next[s] = first[h];      first[h] = s;  }    int find(int i, int j, int s)  {      int h = hash(s);      for(int v = first[h]; v != -1; v = next[v])      {          if(s == sum[v] && st[v].i != i && st[v].i != j && st[v].j != i && st[v].j != j) return 1;      }      return 0;  }    void read_case()  {      init();      for(int i = 0; i < n; i++) scanf("%d", &A[i]);      sort(A, A+n);      for(int i = 0; i < n; i++)      {          for(int j = i+1; j < n; j++)          {              st[rear].i = i, st[rear].j = j;              sum[rear] = A[i]+A[j];              insert(rear);              rear++;          }      }  }    void solve()  {      read_case();      for(int i = n-1; i >= 0; i--)      {          for(int j = 0; j < n; j++) if(i != j)          {              if(find(i, j, A[i]-A[j]))              {                  printf("%d\n", A[i]);                  return ;              }          }      }      printf("no solution\n");  }    int main()  {      while(scanf("%d", &n) && n)      {          solve();      }      return 0;  }

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