Noip 2003 加分二叉树

1.把子树看作区间
2.枚举根
3.小区间转移到大区间，注意边界

#include <algorithm>#include <iostream>#include <cstdio>using namespace std;#define debug(x) cerr << #x << "=" << x << endl;const int MAXN = 50;long long ans;int f[MAXN][MAXN];int bre[MAXN][MAXN], size;int n,a[MAXN];void solve(int l, int r) {    if(l>r)        return;    cout << bre[l][r] << " ";    solve(l,bre[l][r]-1);    solve(bre[l][r]+1,r);}int main() {    cin >> n;    for(int i=1; i<=n; i++) {        cin >> a[i];    }    for(int i=1; i<=n; i++) {        f[i][i] = a[i];        bre[i][i] = i;        f[i][i-1] = 1;    }    for(int r=1; r<=n; r++) {        for(int l=1; l<=n-r; l++) {            for(int k=l; k<l+r; k++) {                if(f[l][k-1] * f[k+1][l+r] + a[k] > f[l][l+r]) {                    f[l][l+r] = f[l][k-1] * f[k+1][l+r] + a[k];                    bre[l][l+r] = k;                    }            }        }    }    cout << f[1][n] << endl;    solve(1,n);    return 0;}