• 《Cracking the Coding Interview》——第3章:栈和队列——题目4


    2014-03-18 05:28

    题目:你肯定听过汉诺威塔的故事:三个柱子和N个从小到大的盘子。既然每次你只能移动放在顶上的盘子,这不就是栈操作吗?所以,请用三个栈来模拟N级汉诺威塔的玩法。放心,N不会很大的。

    解法:递归着玩儿吧,还挺容易写的。要是迭代,我估计够呛。

    代码:

      1 // 3.4 Implement Hanoi Tower with three stacks.
      2 #include <cstdio>
      3 #include <stack>
      4 using namespace std;
      5 
      6 class Solution {
      7 public:
      8     void initHanoiTower(int n) {
      9         int i;
     10         
     11         clearHanoiTower();
     12         
     13         for (i = n; i >= 1; --i) {
     14             s[0].push(i);
     15         }
     16     }
     17     
     18     void moveHanoiTower(int n, int from, int to) {
     19         if (from == to) {
     20             return;
     21         }
     22         
     23         if ((int)s[from].size() < n) {
     24             return;
     25         }
     26         
     27         if (n == 1) {
     28             s[to].push(s[from].top());
     29             s[from].pop();
     30             return;
     31         }
     32         
     33         int i;
     34         for (i = 0; i < 3; ++i) {
     35             b[i] = false;
     36         }
     37         b[from] = true;
     38         b[to] = true;
     39         int other;
     40         for (i = 0; i < 3; ++i) {
     41             if (!b[i]) {
     42                 other = i;
     43                 break;
     44             }
     45         }
     46 
     47         moveHanoiTower(n - 1, from, other);
     48         moveHanoiTower(1, from, to);
     49         moveHanoiTower(n - 1, other, to);
     50     }
     51     
     52     void clearHanoiTower() {
     53         int i;
     54         
     55         for (i = 0; i < 3; ++i) {
     56             while (!s[i].empty()) {
     57                 s[i].pop();
     58             }
     59         }
     60     }
     61     
     62     void printHanoiTower() {
     63         stack<int> ss[3];
     64         int i;
     65         
     66         for (i = 0; i < 3; ++i) {
     67             ss[i] = s[i];
     68             printf("Tower %d:", i + 1);
     69             while (!ss[i].empty()) {
     70                 printf(" %d", ss[i].top());
     71                 ss[i].pop();
     72             }
     73             printf("
    ");
     74         }
     75     }
     76 private:
     77     stack<int> s[3];
     78     int b[3];
     79 };
     80 
     81 int main()
     82 {
     83     int n;
     84     Solution sol;
     85     
     86     while (scanf("%d", &n) == 1 && n > 0) {
     87         sol.initHanoiTower(n);
     88         
     89         printf("At the beginning:
    ");
     90         sol.printHanoiTower();
     91         printf("
    ");
     92 
     93         sol.moveHanoiTower(n, 0, 2);
     94         
     95         printf("At the end:
    ");
     96         sol.printHanoiTower();
     97         printf("
    ");
     98     }
     99     
    100     return 0;
    101 }
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  • 原文地址:https://www.cnblogs.com/zhuli19901106/p/3606714.html
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