hihocoder_week195奖券兑换

题目链接： http://hihocoder.com/contest/hiho195/problem/1

解题思路： 记一下背包问题的模板。

#include <bits/stdc++.h>
using namespace std;

const int imax_n = 100005;
int n, m;
int f[imax_n];
int w[imax_n], p[imax_n];
map<int, int> mp;

void zeroOneBag(int weight, int value)
{
    for (int j = m; j >= weight; --j)
    {
        f[j] = max(f[j], f[j-weight] + value);
    }
}

void completeBag(int weight, int value)
{
    for (int j = weight; j <= m; ++j)
    {
        f[j] = max(f[j], f[j - weight] + value);
    }
}

void multiBag(int weight, int value, int z)
{
    int k = z;
    int b = 1;
    if (k * weight >= m)
    {
        completeBag(weight, value);
        return ;
    }
    while (k >= b)
    {
        zeroOneBag(b*weight, b*value);
        k -= b;
        b<<=1;

    }
    if (k)
        zeroOneBag(k*weight, k*value);
}

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 0; i < n; ++i)
    {
        scanf("%d%d", &w[i], &p[i]);
        mp[100 * w[i] + p[i]]++;
    }
    int ans = 0;
    memset(f, 0, sizeof(f));
    for (int i = 1; i <=10; ++i)
    {
        for (int j = 1; j <=10; ++j)
        {
            if (mp.find(i * 100 + j) == mp.end())
            {
                continue;
            }
            else
            {
                multiBag(i, j, mp[i * 100 + j]);
            }
        }
    }
    for (int i = 0; i <= m; ++i)
    {
        ans = max(ans, f[i]);
    }
    printf("%d\n", ans);
    return 0;
}