Portal
Title description
Give you a string of n length, the difference between the number of'W' and the number of'L' is less than k in the middle, and the difference is exactly k at the end,'D' means a tie,'? 'Is not sure. Ask if such a string exists, output if it exists, and NO if it does not exist.
analysis
Somewhat similar to the writing of digital DP?
Just a memoize search
Code
#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <queue>
#include <map>
#include <cstring>
#define debug(x) cout<<#x<<":"<<x<<endl;
#define _CRT_SECURE_NO_WARNINGS
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> PII;
const int INF = 0x3f3f3f3f;
const int N = 1e4 + 10;
char str[N + 1];
map<int,int> M[N];
int n,m;
bool dfs(int x,int y){
if(x == (n + 1) && abs(y - (n + 1)) == m) return true;
if(x == (n + 1) || abs(y - (n + 1)) >= m) return false;
if(M[x][y]) return false;
M[x][y] = 1;
if(str[x] == 'W') return dfs(x + 1,y + 1);
if(str[x] == 'L') return dfs(x + 1,y - 1);
if(str[x] == 'D') return dfs(x + 1,y);
if(dfs(x + 1,y + 1)) {
str[x] = 'W';
return true;
}
if(dfs(x + 1,y - 1)) {
str[x] = 'L';
return true;
}
if(dfs(x + 1,y)) {
str[x] = 'D';
return true;
}
}
int main(){
scanf("%d%d",&n,&m);
scanf("%s",str + 1);
if(dfs(1,n + 1)) printf("%s",str + 1);
else puts("NO");
return 0;
}
/**
* ┏┓ ┏┓+ +
* ┏┛┻━━━┛┻┓ + +
* ┃ ┃
* ┃ ━ ┃ ++ + + +
* ████━████+
* ◥██◤ ◥██◤ +
* ┃ ┻ ┃
* ┃ ┃ + +
* ┗━┓ ┏━┛
* ┃ ┃ + + + +Code is far away from
* ┃ ┃ + bug with the animal protecting
* ┃ ┗━━━┓ 神兽保佑,代码无bug
* ┃ ┣┓
* ┃ ┏┛
* ┗┓┓┏━┳┓┏┛ + + + +
* ┃┫┫ ┃┫┫
* ┗┻┛ ┗┻┛+ + + +
*/