题目链接:https://codeforces.com/contest/3/problem/C
题目大意:
有一个 \(3 \times 3\) 的棋盘,给你一个棋盘当前的状态,请你输出当前这个状态对应的描述。
解题思路:
\(3 \times 3\) 的棋盘上一共有9个位置,每个位置只有可能是3种状态:“.”、“0”或“X”。
所以总的状态数有 \(3^9\) 种,我们可以从初始状态开始来搜索遍历得到所有的状态对应的描述(如果一个状态通过搜索遍历不到,那么这个状态就是 illegal 的)。
代码解释
get_status_num()
:获得当前状态对应的状态码。
status与状态对应关系:
illegal -- 0
first -- 1
second -- 2
the first player won -- 3
the second player won -- 4
draw -- 5
check_who_win()
:判断当前状态谁赢
- 返回1: the first win
- 返回2:the second win
- 返回0:还没有人赢
check_whos_turn()
:判断当前是应该谁下棋
- 返回1:first
- 返回2:second
最后我们从初始状态搜索一下,就能够得到所有的状态对应的描述。
实现代码如下:
#include <bits/stdc++.h>
using namespace std;
const int maxn = 20000; // 棋盘总共有3^9=19683种状态
char grid[3][4];
int status[maxn];
/**
status与状态对应关系
illegal -- 0
first -- 1
second -- 2
the first player won -- 3
the second player won -- 4
draw -- 5
*/
/*
* get_status_num()获得当前状态对应的状态码
*/
int get_status_num() {
int t = 1, ans = 1;
for (int i = 0; i < 3; i ++) {
for (int j = 0; j < 3; j ++) {
int a;
switch (grid[i][j]) {
case 'X': a = 1; break;
case '0': a = 2; break;
default: a = 0;
}
ans += a * t;
t *= 3;
}
}
return ans;
}
/*
* check_who_win判断当前状态谁赢
* 返回1: the first win
* 返回2:the second win
* 返回0:还没有人赢
*/
int check_who_win() {
for (int i = 0; i < 3; i ++) {
if (grid[i][0]!='.' && grid[i][0]==grid[i][1] && grid[i][0]==grid[i][2]) {
return (grid[i][0] == 'X') ? 1 : 2;
}
if (grid[0][i]!='.' && grid[0][i]==grid[1][i] && grid[0][i]==grid[2][i]) {
return (grid[0][i] == 'X') ? 1 : 2;
}
}
for (int i = -1; i <= 1; i += 2) {
if (grid[1][1]!='.' && grid[1][1]==grid[0][1-i] && grid[1][1]==grid[2][1+i]) {
return (grid[1][1] == 'X') ? 1 : 2;
}
}
return 0;
}
/*
* check_whos_turn判断当前是应该谁下棋
* 返回1:first
* 返回2:second
*/
int check_whos_turn() {
int cnt1 = 0, cnt2 = 0;
for (int i = 0; i < 3; i ++) for (int j = 0; j < 3; j ++) if (grid[i][j] != '.') {
if (grid[i][j] == 'X') cnt1 ++;
else cnt2 ++;
}
if (cnt1 == cnt2) return 1;
else return 2;
}
void init() {
for (int i = 0; i < 3; i ++) for (int j = 0; j < 3; j ++) grid[i][j] = '.';
}
void dfs() {
int status_num = get_status_num();
int winner_id = check_who_win();
if (winner_id) {
status[status_num] = winner_id + 2;
}
else {
int turn_id = check_whos_turn();
status[status_num] = turn_id;
char chess = (turn_id == 1) ? 'X' : '0';
bool has_place_to_put = false;
for (int i = 0; i < 3; i ++) {
for (int j = 0; j < 3; j ++) {
if (grid[i][j] == '.') {
has_place_to_put = true;
grid[i][j] = chess;
dfs();
grid[i][j] = '.';
}
}
}
if (!has_place_to_put) {
status[status_num] = 5; // draw
}
}
}
int main() {
init();
dfs();
for (int i = 0; i < 3; i ++) cin >> grid[i];
string ans;
switch (status[get_status_num()]) {
case 0: ans = "illegal"; break;
case 1: ans = "first"; break;
case 2: ans = "second"; break;
case 3: ans = "the first player won"; break;
case 4: ans = "the second player won"; break;
case 5: ans = "draw"; break;
default: break;
}
cout << ans << endl;
return 0;
}
原文地址:https://www.cnblogs.com/codedecision/p/11690983.html
时间: 2024-10-19 21:01:30