首先有两个问题：

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……一个魔法只有在编号不大于自己的魔法后使用……

那样例2，为什么输出 $-1$，不能连用3个魔法2，威力是14吗

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附加值 $w_{i,j}$ 感觉给反了似乎

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然后我怎么也过不了，甚至写了一个只判可行的代码，结果都判不出来 $-1$

最后交了发题解，题解还能过……

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//我的60分代码
#include <iostream>
#include <cstring>
using namespace std;
const int maxn = 51;
const int move = 0;
const int inf = 2147483647;
int a[maxn], b[maxn], w[maxn][maxn];
int f[maxn][6000];
int main() {
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
	}
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			cin >> w[i][j];
		}
	}
	for (int i = 0; i <= n; i++) {
		for (int j = 0; j <= m + move; j++) {
			f[i][j] = -inf;
		}
	}
	f[0][move] = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = a[i]; j <= m + move; j++) {
			for (int k = 0; k < i; k++) {
				if (f[k][j - a[i]] == -inf) continue;
				f[i][j] = max(f[i][j], f[k][j - a[i]] + b[i] + w[k][i]);
			}
		}
	}
	int ans = -inf;
	for (int i = 1; i <= n; i++) {
		ans = max(ans, f[i][m + move]);
	}
	cout << (ans == -inf? -1 : ans);
	return 0;
}

//判定可行的代码
#include <iostream>
#include <cstring>
using namespace std;
const int maxn = 100;
const int mov = 3000;
int a[maxn], b[maxn];
int can[maxn][6000];
int n, m;
int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
	}
	can[0][mov] = true;
	for (int i = 1; i <= n; i++) {
		for (int k = 0; k < i; k++) {
			for (int j = 0; j <= m + mov; j++) {
				can[i][j] = max(can[i][j], can[k][j - a[i]]);
			}
		}
	}
	for (int i = 0; i <= n; i++) {
		if (can[i][m + mov]) {
			cout << 1;
			return 0;
		}
	}
	cout << -1;
	return 0;
}