UVA 562 Dividing coins

大意不再赘述。

思路：我最开始想通过枚举构造一个背包，往背包里恰好放进多少个硬币，然后求放进背包里的币值与没放进背包里的币值相减的绝对值最小，测试数据与自己写了几组数据全过了，但是为什么会RE呢？？明天再来看看。

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
using namespace std;

const int MAXN = 10100;
const int INF = 0x3f3f3f3f;

typedef long long LL;

LL f[MAXN];
int V[MAXN];

int MIN, totSum;
int n;

void init(int C)
{
	for(int i = 1; i <= C; i++) f[i] = -INF;
	f[0] = 0;
}

int dp(int C)
{
	init(C);
	for(int i = 1; i <= n; i++)
	{
		for(int v = C; v >= V[i]; v--)
		{
			f[v] = max(f[v], f[v-V[i]]+V[i]);
		}
	}
	return f[C];
}

void read_case()
{
	scanf("%d", &n);
	MIN = INF;
	totSum = 0;
	for(int i = 1; i <= n; i++)
	{
		scanf("%d", &V[i]);
		MIN = min(MIN, V[i]);
		totSum += V[i];
	}
}

void solve()
{
	read_case();
	LL ans = INF;
	for(int v = totSum; v >= MIN; v--)
	{
		LL a = dp(v);
		LL dif = abs(2*a-totSum); //差的绝对值 
		ans = min(ans, dif);
	}
	printf("%lld\n", ans);
}

int main()
{ 
	int T;
	scanf("%d", &T);
	while(T--)
	{
		solve();
	}
}