打气球dfs

来源：互联网发布：c语言程序编程教学编辑：程序博客网时间：2024/05/09 20:48

package xj;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class DaQiqiu {
static int T, N, maxsum;
static int data[];
static int num[];
static boolean used[];

public static void main(String[] args) throws FileNotFoundException {
  /* Scanner sc=new Scanner(System.in); */
  Scanner sc = new Scanner(new File("src/DaQiqiu"));
  T = sc.nextInt();
  for (int t = 0; t < T; t++) {
   N = sc.nextInt();
   data = new int[N];
   used = new boolean[N];
   num=new int[N];
   for (int i = 0; i < N; i++) {
    data[i] = sc.nextInt();
   }
   maxsum = 0;
    dfs(0,0);

   /*
    * for (int i = 0; i < N; i++) { System.out.print(" "+data[i]); }
    */

System.out.println(maxsum);
}
}

private static void dfs(int step, int sum) {
  if (step == N) {
   if (maxsum < sum) {
    maxsum = sum;
   }
   return;
  }
  for (int i = 0; i < N; i++) {

   if (!used[i]) {
    int l = -1;
    int r = -1;
    int t = sum;
    // you
    for (int j = i + 1; j < N; j++) {//这里一开始弄混淆了i和step
     if (!used[j]) {
      r = j;
      break;
     }
    }
    // zuo
    for (int j = i - 1; j >= 0; j--) {
     if (!used[j]) {
      l = j;
      break;
     }
    }
    //
    if (l == -1 && r != -1) {
     sum += data[r];
    }
    //
    if (l != -1 && r == -1) {
     sum += data[l];
    }
    //
    if (l != -1 && r != -1) {
     sum += data[l] * data[r];
    }
    //
    if (l == -1 && r == -1) {
     sum += data[i];
    }
    used[i] = true;
    dfs(step + 1, sum);
    used[i] = false;
    sum = t;
   }
  }
}
}

//input

7
5
3 10 1 2 5
7
12 48 28 21 67 75 85
6
2 3 4 6 7 1
4
1 2 3 4
10
1 2 1 4 5 6 7 8 9 10
5
1 2 3 4 5
3
2 8 3

//output

100
16057
84
20
360
40
24

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