Questions by Aravind

access_rights.md

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+---
+title: Access rights
+---
+
+# Problem Statement
+
+You are trying to create a permission based filesystem access for the new unix-inspired Operating System you are developing. The requirements for this system is as given below.
+
+For each file there is a known set of operations which may be applied to it:
+write W,
+read R,
+execute X.
+
+The first line contains the number N — the number of files contained in the filesystem. The following N lines contain the file names and allowed operations with them, separated by spaces. The next line contains an integer M — the number of operations to the files. In the last M lines specify the operations that are requested for files. One file can be requested many times.
+
+For each request your program should return OK if the requested operation is valid or Access denied if the operation is invalid.
+
+**Input Format:** An integer N, followed by N lines containing the file names and permissions. Then an integer M on the next line, followed by M lines specifying operation requests on the files.
+
+**Output Format:** The response to each of the M requests, one per line, print `OK` if the requested operation is allowed or `Access denied` if it is disallowed.
+
+## Sample Input
+```
+4
+helloworld.exe R X
+pinglog W R
+nya R
+goodluck X W R
+5
+read nya
+write helloworld.exe
+execute nya
+read pinglog
+write pinglog
+```
+## Sample Output
+```
+OK
+Access denied
+Access denied
+OK
+OK
+```
+
+# Solution
+```python test.py  -r 'python test.py'
+<template>
+<sol>
+permissions = {}
+n = int(input())
+for i in range(n):
+    s = input().split()
+    permissions[s[0]] = set(s[1:])
+for i in range(int(input())):
+    operation, file = input().split()
+    permission = None
+    if operation == 'read':
+        permission = 'R'
+    if operation == 'write':
+        permission = 'W'
+    if operation == 'execute':
+        permission = 'X'
+    if permission in permissions[file]:
+        print('OK')
+    else:
+        print('Access denied')
+</sol>
+</template>
+```
+
+# Public Test Cases
+
+## Input 1
+
+```
+4
+helloworld.exe R X
+pinglog W R
+nya R
+goodluck X W R
+5
+read nya
+write helloworld.exe
+execute nya
+read pinglog
+write pinglog
+```
+
+## Output 1
+
+```
+OK
+Access denied
+Access denied
+OK
+OK
+```
+
+
+## Input 2
+
+```
+1
+abacaba X
+3
+read abacaba
+write abacaba
+execute abacaba
+```
+
+## Output 2
+
+```
+Access denied
+Access denied
+OK
+```
+
+
+## Input 3
+
+```
+1
+tmp_909925047 W X R
+7
+execute tmp_909925047
+read tmp_909925047
+write tmp_909925047
+read tmp_909925047
+execute tmp_909925047
+execute tmp_909925047
+read tmp_909925047
+```
+
+## Output 3
+
+```
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+```
+
+
+# Private Test Cases
+
+## Input 1
+
+```
+5
+tmp_1017722015 W
+tmp_897110090 X W R
+tmp_651548400 W X
+tmp_422551574 X R W
+tmp_477658548 W
+1
+write tmp_897110090
+```
+
+## Output 1
+
+```
+OK
+```
+
+## Input 2
+
+```
+2
+tmp_584361681 R X
+tmp_70361076 X
+3
+read tmp_70361076
+write tmp_70361076
+write tmp_70361076
+```
+
+## Output 2
+
+```
+Access denied
+Access denied
+Access denied
+```
+
+## Input 3
+
+```
+4
+tmp_796487715 X R W
+tmp_31144126 X R
+tmp_967334538 R
+tmp_264755563 R W
+3
+read tmp_264755563
+execute tmp_796487715
+execute tmp_796487715
+```
+
+## Output 3
+
+```
+OK
+OK
+OK
+```