CodeForces 837D - Round Subset | Educational Codeforces Round 26

/*
CodeForces 837D - Round Subset [ DP ]  |  Educational Codeforces Round 26
题意：
	选k个数相乘让末尾0最多
分析：
	第i个数字有a[i]个2, b[i] 个5
	以其中一维作体积另一维作价值01背包即可
*/
#include <bits/stdc++.h>
using namespace std;
int dp[205][20005];
int get2(long long x)
{
    int s = 0;
    while (x % 2 == 0) s++, x /= 2;
    return s;
}
int get5(long long x)
{
    int s = 0;
    while (x % 5 == 0) s++, x /= 5;
    return s;
}
int n, k;
int main()
{
    scanf("%d%d", &n, &k);
    memset(dp, -1, sizeof(dp));
    dp[0][0] = 0;
    for (int i = 1; i <= n; i++)
    {
        long long x; scanf("%lld", &x);
        int a = get2(x);
        int b = get5(x);
        for (int j = k; j >= 1; j--)
            for (int p = a; p <= 20000; p++)
                if (dp[j-1][p-a] != -1)
                    dp[j][p] = max(dp[j][p], dp[j-1][p-a] + b);
    }
    int ans = 0;
    for (int i = 1; i <= 20000; i++)
        if (dp[k][i] != -1)
            ans = max(ans, min(i, dp[k][i]));
    printf("%d\n", ans);
}