牛客,小红不想做完全背包
https://ac.nowcoder.com/acm/contest/78904/D
题意:n个物品,求物品的价值和为p的倍数的方案中,最少几件物品。
思路:完全背包,将背包容量从p扩大到p的20倍,可以直接ac。
看了题解,发现用bfs做的,感觉逻辑也还行。
想尝试用物品预处理出所有可能的余数,并记录到达该余数的最小数量值,然后当背包处理。但是不知道为什么不能ac,代码先贴上。
void solve(){
int n, p;
cin >> n >> p;
const int inf = 0x3f3f3f3f;
vector<int> weights(p + 1, inf);
for (int i = 1; i <= n; ++i){
long long value;
cin >> value;
value %= p;
weights[value] = 1;
int k = 2;
while (k < p){
int cur = value * k % p;
//cout << cur << " " << k << " " << weights[cur] << endl;
weights[cur] = min(weights[cur], k);
k ++;
//cout << cur << " " << k << " " << weights[cur] << endl;
}
}
//for (int i = 0; i <= p; ++i){cout << weights[i] << " \n"[i == p];}
vector<int> dp = weights;
dp[0] = 0;
dp[p] = weights[0];
for (int i = 1; i < p; ++i){
if (weights[i] == inf){
continue;
}
for (int j = i; j <= p; ++j){
dp[j] = min(dp[j], dp[j - i] + min(weights[i], dp[i]));
}
}
cout << dp[p] << endl;
// for (int i = 0; i <= p; ++i){cout << weights[i] << " \n"[i == p];}
}

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