[背包DP] 洛谷P1757 分组背包

题目

LP1757

思路

背包九讲

代码

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <utility>
#define _for(i,a,b) for(int i = (a); i<(b); i++)
#define _rep(i,a,b) for(int i = (a); i<=(b); i++)
using namespace std;

const int maxm = 1000 + 10;
const int maxt = 100 + 10;
int n, c, v, w, d[maxm];
vector<pair<int, int> > item[maxt];

int main() {
    scanf("%d%d", &c, &n);
    int s, t = 0;
    _for(i, 0, n) {
        scanf("%d%d%d", &v, &w, &s);
        s--;
        if (item[s].empty()) t++;
        item[s].push_back(make_pair(v, w));
    }

    _for(i, 0, t) {
        for (int j = c; j >= 0; j--)
            for (vector<pair<int, int> >::iterator iter = item[i].begin(); iter != item[i].end(); ++iter)
                if (j >= (*iter).first)
                    d[j] = max(d[j], d[j - (*iter).first] + (*iter).second);
    }

    int ans = 0;
    _rep(i, 0, c) ans = max(ans, d[i]);
    printf("%d\n", ans);

    return 0;
}