8/7/23

- EPI: Apply permuation (Python/CPP)
- EPI: Convert int to string and vice versa (Python/CPP)
- Anki update

Author: jsgoller1

.vscode/settings.json

@@ -59,7 +59,74 @@
         "format": "cpp",
         "stacktrace": "cpp",
         "__locale": "cpp",
-        "locale": "cpp"
+        "locale": "cpp",
+        "__bits": "cpp",
+        "__config": "cpp",
+        "__debug": "cpp",
+        "__errc": "cpp",
+        "__mutex_base": "cpp",
+        "__node_handle": "cpp",
+        "__nullptr": "cpp",
+        "__string": "cpp",
+        "__threading_support": "cpp",
+        "__tuple": "cpp",
+        "atomic": "cpp",
+        "barrier": "cpp",
+        "bit": "cpp",
+        "bitset": "cpp",
+        "cctype": "cpp",
+        "cfenv": "cpp",
+        "cinttypes": "cpp",
+        "clocale": "cpp",
+        "codecvt": "cpp",
+        "concepts": "cpp",
+        "condition_variable": "cpp",
+        "csetjmp": "cpp",
+        "csignal": "cpp",
+        "cstdarg": "cpp",
+        "cstddef": "cpp",
+        "cstdint": "cpp",
+        "cstdio": "cpp",
+        "cstdlib": "cpp",
+        "cstring": "cpp",
+        "ctime": "cpp",
+        "cwchar": "cpp",
+        "cwctype": "cpp",
+        "exception": "cpp",
+        "coroutine": "cpp",
+        "fstream": "cpp",
+        "future": "cpp",
+        "iomanip": "cpp",
+        "ios": "cpp",
+        "istream": "cpp",
+        "latch": "cpp",
+        "limits": "cpp",
+        "memory": "cpp",
+        "mutex": "cpp",
+        "new": "cpp",
+        "numbers": "cpp",
+        "numeric": "cpp",
+        "optional": "cpp",
+        "ostream": "cpp",
+        "queue": "cpp",
+        "semaphore": "cpp",
+        "sstream": "cpp",
+        "stack": "cpp",
+        "stdexcept": "cpp",
+        "streambuf": "cpp",
+        "typeindex": "cpp",
+        "typeinfo": "cpp",
+        "algorithm": "cpp",
+        "*.tcc": "cpp",
+        "cuchar": "cpp",
+        "expected": "cpp",
+        "iterator": "cpp",
+        "shared_mutex": "cpp",
+        "spanstream": "cpp",
+        "stdfloat": "cpp",
+        "stop_token": "cpp",
+        "syncstream": "cpp",
+        "thread": "cpp"
     },
     "[python]": {
         "editor.defaultFormatter": "ms-python.autopep8"

anki/Competitive Programming.apkg

@@ -2,10 +2,43 @@
 
 #include "test_framework/generic_test.h"
 using std::vector;
+void ApplyPermutationLinearSpace(vector<int> perm, vector<int>* A_ptr) {
+  vector<int>& A = *A_ptr;
+  vector<int> result(A.size(), 0);
+  for (int i = 0; i < perm.size(); i++) {
+    int idx = perm[i];
+    result[idx] = A[i];
+  }
+  for (int i = 0; i < result.size(); i++) {
+    A[i] = result[i];
+  }
+  return;
+}
+
 void ApplyPermutation(vector<int> perm, vector<int>* A_ptr) {
-  // TODO - you fill in here.
+  vector<int>& A = *A_ptr;
+  if (A.size() == 0) {
+    return;
+  }
+  int idx = 0;
+  int curr = A[idx];
+  for (int i = 0; i < perm.size(); i++) {
+    int newIdx = perm[i];
+    if (newIdx == -1) {
+      continue;
+    }
+    while (newIdx != -1) {
+      int next = A[newIdx];
+      A[newIdx] = curr;
+      curr = next;
+      perm[idx] = -1;
+      idx = newIdx;
+      newIdx = perm[newIdx];
+    }
+  }
   return;
 }
+
 vector<int> ApplyPermutationWrapper(const vector<int>& perm, vector<int> A) {
   ApplyPermutation(perm, &A);
   return A;

elements-of-programming-interviews/cpp/apply_permutation.cc

@@ -4,14 +4,39 @@
 #include "test_framework/test_failure.h"
 using std::string;
 
+#define ASCII_ZERO 48
+
 string IntToString(int x) {
-  // TODO - you fill in here.
-  return "0";
+  if (!x) {
+    return "0";
+  }
+  bool neg = (x < 0);
+  string val;
+  while (x) {
+    int digit = abs(x % 10) + ASCII_ZERO;
+    val += digit;
+    x /= 10;
+  }
+  if (neg) {
+    val += "-";
+  }
+  reverse(val.begin(), val.end());
+  return val;
 }
+
 int StringToInt(const string& s) {
-  // TODO - you fill in here.
-  return 0;
+  bool neg = (s[0] == '-');
+  bool skipFirstChar = neg || (s[0] == '+');
+  unsigned place = 1;
+  int total = 0;
+  for (int i = s.length() - 1; i >= (skipFirstChar ? 1 : 0); i--) {
+    char digit = s[i] - ASCII_ZERO;
+    total += (digit * place);
+    place *= 10;
+  }
+  return total * (neg ? -1 : 1);
 }
+
 void Wrapper(int x, const string& s) {
   if (stoi(IntToString(x)) != x) {
     throw TestFailure("Int to string conversion failed");

elements-of-programming-interviews/cpp/string_integer_interconversion.cc

@@ -312,15 +312,15 @@ problem_mapping = {
         },
         "5.10 Permute the elements of an array": {
             "C++: apply_permutation.cc": {
-                "passed": 0,
+                "passed": 101,
                 "total": 101
             },
             "Java: ApplyPermutation.java": {
                 "passed": 0,
                 "total": 101
             },
             "Python: apply_permutation.py": {
-                "passed": 0,
+                "passed": 101,
                 "total": 101
             }
         },
@@ -482,15 +482,15 @@ problem_mapping = {
         },
         "6.01 Interconvert strings and integers": {
             "C++: string_integer_interconversion.cc": {
-                "passed": 0,
+                "passed": 15002,
                 "total": 15002
             },
             "Java: StringIntegerInterconversion.java": {
                 "passed": 0,
                 "total": 15002
             },
             "Python: string_integer_interconversion.py": {
-                "passed": 0,
+                "passed": 15002,
                 "total": 15002
             }
         },

elements-of-programming-interviews/problem_mapping.js

@@ -4,7 +4,18 @@
 
 
 def apply_permutation(perm: List[int], A: List[int]) -> None:
-    # TODO - you fill in here.
+    for i, idx in enumerate(perm):
+        if idx == -1:
+            continue
+        val = A[idx]
+        nextIdx = perm[idx]
+        while nextIdx != -1:
+            nextVal = A[nextIdx]
+            A[nextIdx] = val
+            val = nextVal
+            perm[idx] = -1
+            idx = nextIdx
+            nextIdx = perm[idx]
     return
 
 

elements-of-programming-interviews/python/apply_permutation.py

@@ -3,13 +3,26 @@
 
 
 def int_to_string(x: int) -> str:
-    # TODO - you fill in here.
-    return '0'
+    if not x:
+        return "0"
+    neg = "-" if x < 0 else ""
+    x = x*-1 if neg else x
+    string = []
+    while x:
+        string.append(str(x % 10))
+        x //= 10
+    return neg + "".join(string[::-1])
 
 
 def string_to_int(s: str) -> int:
-    # TODO - you fill in here.
-    return 0
+    place = 1
+    val = 0
+    neg = s[0] == "-"
+    s = s[1:] if neg or s[0] == "+" else s
+    for char in s[::-1]:
+        val += int(char) * place
+        place *= 10
+    return val * -1 if neg else val
 
 
 def wrapper(x, s):
@@ -20,7 +33,11 @@ def wrapper(x, s):
 
 
 if __name__ == '__main__':
+    # print(int_to_string(0))
+    # print(string_to_int("0"))
+    # """
     exit(
         generic_test.generic_test_main('string_integer_interconversion.py',
                                        'string_integer_interconversion.tsv',
                                        wrapper))
+    # """