1 #include<stdio.h>//二分搜索技术运用。此题在排序后应用减法从右往左。
2 #include<stdlib.h>
3 #include<string.h>
4
5 int a[1001],i,j,k,ncases;
6 int search(int num,int from,int end)
7 {
8 int mid;
9 while(from <= end)
10 {
11 mid = (from+end)/2;
12 if(num == a[mid])
13 return 1;
14 if(num < a[mid])
15 end = mid-1;
16 else
17 from = mid+1;
18 }
19 return 0;
20 }
21
22 int cmp(const void *a,const void *b)
23 {
24 return *(int *)a - *(int *)b;
25 }
26
27 int main()
28 {
29 int sum,tmp,flag;
30
31 while(scanf("%d",&ncases)&&ncases)
32 {
33 for(i=0; i<ncases; i++)
34 {
35 scanf("%d",&a[i]);
36 }
37 qsort(a,ncases,sizeof(a[0]),cmp);
38 flag = 0;
39 for(i=ncases-1; i>=0; i--)
40 {
41 for(j=ncases-1; j>=0; j--)
42 {
43 if(i == j) continue;
44 tmp = a[i] - a[j];
45 for(k=ncases-1; k>=0; k--)
46 {
47 if(i==k || j==k)
48 continue;
49 sum = tmp - a[k];
50 if(sum==a[i] || sum==a[j] || sum==a[k])//防止重复
51 continue;
52 if(search(sum,0,ncases-1))
53 {
54 printf("%d\n",a[i]);
55 flag = 1;
56 goto H;
57 }
58 }
59 }
60 }
61 if( !flag )
62 printf("no solution\n");
63 H: if(flag==1) continue;
64 }
65
66 return 0;
67 }
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