POJ1948 Triangular Pastures

POJ1948 Triangular Pastures

 #include <iostream>
 #include <cmath>
 using namespace std;
 const int maxn = ;
 bool dp[maxn][maxn];
 int a[maxn];
 double area(double a, double b, double c) {
     double p = (a+b+c)/;
     return sqrt(p*(p-a)*(p-b)*(p-c));
 }
 bool is_ok(int a, int b, int c) {
     if (a+b <= c || a+c <= b || b+c <= a)
         return false;
     return true;
 }
 int main() {
     int n; cin >> n;
     int sum = ;
     for (int i = ; i < n; i++) {
         cin >> a[i];
         sum += a[i];
     }
     dp[][] = true;
     for (int i = ; i < n; i++) {
         for (int k = ; k >= ; k--) {
             for (int j = k; j >= ; j--) {
                 if (k-a[i] >=  && dp[k-a[i]][j])
                     dp[k][j] = true;
                 if (j-a[i] >=  && dp[k][j-a[i]])
                     dp[k][j] = true;
             }
         }
     }
 
     double ans = ;
     for (int i = ; i <= ; i++) {
         for (int j = ; j <= i; j++) {
             if (dp[i][j] && is_ok(i,j,sum-i-j))
                 ans = max(ans,*area(i,j,sum-i-j));
         }
     }
     if (ans == ) cout << - << endl;
     else cout << (int)ans << endl;
     return ;
 }