DFS之奇偶剪枝

Tempter of the Bone Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 92175    Accepted Submission(s): 25051 Problem Description The doggie found a bone in an ancient maze, which fascinated him a

题目链接:点击打开链接 题目描述:给定一个迷宫,给一个起点和一个终点,问能否恰好经过T步到达终点?每个格子不能重复走 解题思路:dfs+剪枝 剪枝1:奇偶剪枝,判断终点和起点的距离与T的奇偶性是否一致,如果不一致,直接剪掉 剪枝2:如果从当前到终点的至少需要的步数nt加上已经走过的步数ct大于T,即nt+ct>t剪掉 剪枝3:如果迷宫中可以走的格子小于T直接剪掉 启发:剪枝的重要性 代码: #include <cstdio> #include <cstdlib> #inclu

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1010 题目描述:在n*m的矩阵中,有一起点和终点,中间有墙,给出起点终点和墙,并给出步数,在该步数情况下走到终点,走过的点不能再走: 题目要点:dfs+奇偶剪枝:输入: 本题用dfs可以做出结果,但是会超时,需要用到就剪枝,来减去大部分的可能: 奇偶剪枝: 方格中起点(tx,ty)和终点(dx, dy)最小步骤是minstep=abs(tx-dx)+abs(ty-dy); 给定步数t,从起点走到终点

Tempter of the Bone Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 74916    Accepted Submission(s): 20481 Problem Description The doggie found a bone in an ancient maze, which fascinated him a

奇偶剪枝: 对于从起始点 s 到达 终点 e,走且只走 t 步的可达性问题的一种剪枝策略. 如下列矩阵 : 从任意 0 到达 任意 0,所需步数均为偶数,到达任意 1 ,均为奇数.反之亦然 所以有,若s走且只走 t 步可到达e,则必有t >= abs(s.x - e.x) + abs(s.y - e.y),且 (t&1) == ((abs(s.x - e.x) + abs(s.y - e.y))&1). 否则必不可达. #include <iostream> #inclu

Tempter of the Bone Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 75141    Accepted Submission(s): 20531 Problem Description The doggie found a bone in an ancient maze, which fascinated him a

Tempter of the Bone Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 125945    Accepted Submission(s): 33969 Problem Description The doggie found a bone in an ancient maze, which fascinated him a

Tempter of the Bone Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 89317    Accepted Submission(s): 24279 Problem Description The doggie found a bone in an ancient maze, which fascinated him a

Problem Description: The doggie found a bone in an ancient maze, which fascinated him a lot. However, when he picked it up, the maze began to shake, and the doggie could feel the ground sinking. He realized that the bone was a trap, and he tried desp