SRM 582 Div II Level Three： ColorTheCells, Brute Force 算法

#include <iostream>
#include <vector>
#include <limits>
#include <algorithm>

using namespace std;

class ColorTheCells
{
private:
vector <int> dryingTime;	/* 需要干燥的时间  */
vector <long> dryedTime;	/* 正好干燥的时间，0表示还没有paint */
vector <int> paint_order;	/* paint格子的顺序 */
public:
long calc(int seq);
int minimalTime(vector <int> dryingTime);
};

#define MOVE_TIME 1L
#define PAINT_TIME 1L
#define INFINITY_TIME LONG_MAX

/* 参考Ueddy代码实现 */
int ColorTheCells::minimalTime(vector<int> dryingTime)
{
int num = dryingTime.size();
long minTime = INFINITY_TIME;
int i, j;

this->dryingTime = dryingTime;
paint_order.clear();		/* paint 的顺序 */
dryedTime.clear();

for (i = 0; i < num; i++) {
paint_order.push_back(i);
dryedTime.push_back(0);
}

/* brute force，枚举所有的情况，选出最小时间 */
do {
for (i = 0; i < (1<<num); i++) {
for (j = 0; j < num; j++) {
dryedTime[j] = 0;
}
minTime = min(minTime, calc(i));
}
} while (next_permutation(paint_order.begin(), paint_order.end()));

return minTime;
}

/**
* seq为一个序列，0表示在被paint位置左边paint, 1表示在右边paint，paint的顺序由
* paint_order指定。
*/
long ColorTheCells::calc(int seq)
{
long time;			/* 所用时间 */
int num = dryingTime.size();
int paint_dir;			/* paint方向，在被paint位置左边还是右边paint */
int cur_pos;			/* 当前位置 */
int paint_pos;			/* paint位置，不是被paint的位置 */
int bias;			/* 从当前位置向左走还是向右走 */

cur_pos = 0;
time = 0;
for (int i = 0; i < num; i++) {
paint_dir = seq & 1;
seq /= 2;
paint_dir = paint_dir ? 1 : -1;
paint_pos = paint_order[i] + paint_dir;
if (paint_pos < 0 || paint_pos >= num) {	/* 位置不合法 */
return INFINITY_TIME;
}

bias = 1;			/* 从当前位置向右走 */
if (cur_pos - paint_pos > 0) {	/* 从当前位置向左走 */
bias = -1;
}

/* 用for循环到达paint位置，中间遇到还没有干燥的格子要等待 */
for (; cur_pos != paint_pos; cur_pos += bias) {
if (dryedTime[cur_pos+bias] > time) {	/* 等待干燥 */
time = dryedTime[cur_pos+bias];
}
time += MOVE_TIME;		/* 移动时间 */
}
time += PAINT_TIME;		/* 到达目的地，paint时间 */
dryedTime[paint_order[i]] = time + dryingTime[paint_order[i]];	/* 更新该格子干燥时间  */
}

return time;
}