[51NOD1007] 正整数分组（DP，记忆化搜索）

题目链接：http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1007

dp(id, s)表示第id个数之前，其中一个集合和为s的差，按照取和不取dfs就行。

#include <bits/stdc++.h>
using namespace std;

const int maxn = 110;
const int maxm = 11000;
const int inf = 100100100;
int n;
int a[maxn], sum;
int dp[maxn][maxm];

int dfs(int id, int s) {
  if(id == n+1) return abs(s-(sum-s));
  if(~dp[id][s]) return dp[id][s];
  return dp[id][s] = min(dfs(id+1, s), dfs(id+1, s+a[id]));
}

int main() {
  // freopen("in", "r", stdin);
  while(~scanf("%d", &n)) {
    memset(dp, -1, sizeof(dp));
    sum = 0;
    for(int i = 1; i <= n; i++) {
      scanf("%d", &a[i]);
      sum += a[i];
    }
    printf("%d
", dfs(1, 0));
  }
  return 0;
}