poj1717

两次记忆化搜索，第一次找最小的gap，第二次找最少的次数。

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
int n,x;
int a[1005];
int b[1005];
int dp[1005][6005];
int abs(int a)
{
    return a > 0 ? a : -a;
}
int dfs(int cur,int gap)
{
    if(dp[cur][gap] != -1)
        return dp[cur][gap];
    if(cur == n)
    {
        return dp[cur][gap] = abs(gap);
    }
    int x = dfs(cur + 1,gap + a[cur] - b[cur]);
    int y = dfs(cur + 1,gap + b[cur] - a[cur]);
    return dp[cur][gap] = min(x, y);
}
int dfs2(int cur,int gap)
{
    if(dp[cur][gap] != -1)
        return dp[cur][gap];
    if(cur == n)
    {
        if(abs(gap) == x)
            return dp[cur][gap] = 0;
        return dp[cur][gap] = INF;
    }
    int p = dfs2(cur + 1,gap + a[cur] - b[cur]);
    int q = dfs2(cur + 1,gap + b[cur] - a[cur]) + 1;
    return dp[cur][gap] = min(p, q); 
}
int main()
{
    cin >> n;
    for(int i = 0;i < n;i ++)
    {
        scanf("%d%d",&a[i],&b[i]);
    }
    memset(dp,-1,sizeof(dp));
    x = dfs(0,0);
    memset(dp,-1,sizeof(dp));
    cout << dfs2(0,0) << endl;
    return 0;    
}