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  • Codeforces 1079 E

    E - The Unbearable Lightness of Weights

    思路:

    分组背包dp

    每组最多只能选一个

    一些优化可以快很多

    代码:

    #pragma GCC optimize(2)
    #pragma GCC optimize(3)
    #pragma GCC optimize(4)
    #include<bits/stdc++.h>
    using namespace std;
    #define fi first
    #define se second
    #define pi acos(-1.0)
    #define LL long long
    //#define mp make_pair
    #define pb push_back
    #define ls rt<<1, l, m
    #define rs rt<<1|1, m+1, r
    #define ULL unsigned LL
    #define pll pair<LL, LL>
    #define pli pair<LL, int>
    #define pii pair<int, int>
    #define piii pair<pii, int>
    #define mem(a, b) memset(a, b, sizeof(a))
    #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);
    //head
    
    const int N = 105, M = 1e4 + 5;
    int cnt[N];
    int dp[N][M];
    int main() {
        int n, a;
        scanf("%d", &n);
        for (int i = 1; i <= n; i++) scanf("%d", &a), cnt[a]++;
        
        dp[0][0] = 1;
        int dif = 0, tot = 0, sum = 0;
        for (int i = 1; i < N; i++) {
            if(cnt[i]) {
                tot += cnt[i];
                sum += cnt[i]*i;
                for (int j = sum; j >= i; j--) {
                    for (int k = 1; k <= cnt[i]; k++) {
                        if(j < k*i) break;
                        for (int l = k; l <= tot; l++) {
                            dp[l][j] = min(dp[l][j]+dp[l-k][j-k*i], 2);
                        }
                    }
                }    
                dif++;    
            }
        } 
        
        if(dif <= 2) return 0*printf("%d
    ", n);
        int ans = 1;
        for (int i = 1; i < N; i++) {
            if(cnt[i]) {
                for (int j = 1; j <= cnt[i]; j++) if(dp[j][j*i] == 1) ans = max(ans, j);
            }
        }
        printf("%d
    ", ans);
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/widsom/p/9998721.html
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