Sumsets Uva10125 poj

//3sum问题

#include <iostream>#include <cstdio>#include <cstdlib>#include <cmath>#include <queue>#include <algorithm>#include <vector>#include <cstring>#include <stack>#include <cctype>#include <utility>   #include <map>#include <string>  #include <climits> #include <set>#include <string> #include <sstream>#include <utility>#include <ctime>using std::priority_queue;using std::vector;using std::swap;using std::stack;using std::sort;using std::max;using std::min;using std::pair;using std::map;using std::string;using std::cin;using std::cout;using std::set;using std::queue;using std::string;using std::istringstream;using std::make_pair;using std::greater;const int MAXN(1010);int arr[MAXN];int main(){int n;while(scanf("%d", &n), n){for(int i = 1; i <= n; ++i)scanf("%d", arr+i);sort(arr+1, arr+1+n);int count = 0;for(int i = 1; i <= n; ++i)if(i == 1 || arr[i] != arr[i-1])arr[++count] = arr[i];int ans;try{int tn = n-2;for(int i = n; i >= 1; --i){ans = arr[i];for(int j = 1; j <= tn; ++j)if(j != i){int l = j+1, r = n;while(l < r){if(l == i){++l;continue;}if(r == i){--r;continue;}int temp = arr[j]+arr[l]+arr[r];if(temp == ans)throw true;if(temp > ans)--r;else++l;}}}printf("no solution\n");}catch(bool){printf("%d\n", ans);}}return 0;}