[luoguP1877] [HAOI2012]音量调节（DP）

#include <cstdio>
#include <iostream>
#define N 51

int n, s, mx;
bool f[N][1001];

inline int read()
{
	int x = 0, f = 1;
	char ch = getchar();
	for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;
	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;
	return x * f;
}

int main()
{
	int i, j, k, x;
	n = read();
	s = read();
	mx = read();
	f[0][s] = 1;
	for(i = 1; i <= n; i++)
	{
		x = read();
		for(j = 0; j <= mx; j++)
		{
			if(j + x <= mx && f[i - 1][j]) f[i][j + x] = 1;
			if(j - x >= 0 && f[i - 1][j]) f[i][j - x] = 1;
		}
	}
	for(i = mx; i >= 0; i--)
		if(f[n][i])
		{
			printf("%d\n", i);
			return 0;
		}
	puts("-1");
	return 0;
}