第5章 回溯法，批处理作业调度

#include <iostream>
#include <cstdio>

using namespace std;

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MAXSIZE 10
#define INF 999999999

struct Job_Info
{
	int t1, t2;
}job[MAXSIZE];
int n;						//作业数量
int solu[MAXSIZE];			//调度次序
int optimalValue;			//最优值
int optimalSolu[MAXSIZE];	//最优解

void Swap(int &a, int &b)
{
	int temp = a;
	a = b;
	b = temp;
}

//time1，time2分别为机器1和机器2的完成处理时间
//totalTime为已完成作业的时间和
void Backtrack(int k, int time1, int time2, int totalTime)
{
	int i;
	if (k >= n)
	{
		for (i = 0; i < n; i++)
		{
			optimalSolu[i] = solu[i];
		}
		optimalValue = totalTime;
	}
	else
	{
		for (i = k; i < n; i++)
		{
			//计算完成第i个任务后，两机器的时间
			int nextTime1 = time1 + job[solu[i]].t1;
			int nextTime2 = MAX(nextTime1, time2) + job[solu[i]].t2;
			//已完成作业的时间和是否小于最优值
			if (totalTime + nextTime2 < optimalValue)
			{
				Swap(solu[k], solu[i]);
				Backtrack(k+1, nextTime1, nextTime2, totalTime+nextTime2);
				Swap(solu[k], solu[i]);
			}
		}
	}
}

int main(void)
{
	int i;
	for (i = 0; i < MAXSIZE; i++)
	{
		solu[i] = i;
	}
	while (scanf("%d", &n) != EOF)
	{
		for (i = 0; i < n; i++)
		{
			scanf("%d%d", &job[i].t1, &job[i].t2);
		}

		optimalValue = INF;
		Backtrack(0, 0, 0, 0);

		printf("optimal value: %d\n", optimalValue);
		printf("optimal solution: ");
		for (i = 0; i < n-1; i++)
		{
			printf("%d ", optimalSolu[i]+1);
		}
		printf("%d\n", optimalSolu[i]+1);
	}
	return 0;
}