JZOJ 2679. Era-like pressure dp [] [] [backpack] [dfs 7.6 A group T1]

Subject to the effect:

To n of length l [i] of claim fence surrounded a maximum area rectangle may not] [fence

Problem-solving ideas:

Elongate side pressure can be composed
then search storm

$Accepted\ code:$

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

int n, ans;
int l[16], f[10000], a[1<<17];

void dp(int sum, int x) {
    if (sum & 1) return;
    for (int i = 0; i < n; ++i)
	if (x & (1<<i)) {
		for (int j = sum; j >= l[i]; --j)
			if (f[j-l[i]] != 0) f[j] = 1;
	}
    if (f[sum>>1] != 0) a[x] = 1;
}

void dfs(int x, int len1, int y, int len2, int deep) {
    if (deep == n) {
        if (a[x] && a[y]) ans = max(ans, (len1*len2) >> 2);
        return;
    }
    dfs(x, len1, y, len2, deep + 1);
	dfs(x + (1<<deep), len1 + l[deep], y, len2, deep + 1);
	dfs(x, len1, y + (1<<deep), len2 + l[deep], deep + 1);
}

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; ++i)
		scanf("%d", &l[i]);
    for (int i = 1; i < (1 << n); ++i) {
        int sum = 0;
        for (int j = 0; j < n; ++j) 
			if (i & (1<<j)) sum += l[j];
		memset(f, 0, sizeof(f));
		f[0] = 1;
        dp(sum, i);
    }
    dfs(0, 0, 0, 0, 0);
    if (ans != 0) printf("%d", ans);
	else printf("No Solution");
    return 0;
}