leetcode

Author: ayoubzulfiqar

StringToInteger/string_to_integer.go

@@ -0,0 +1,55 @@
+package main
+
+func myAtoi(s string) int {
+if len(s) == 0 {
+return 0
+}
+
+sign := 1 // -1 negative
+index := 0
+val := 0
+
+for len(s) > index && s[index] == ' ' {
+index++
+}
+
+if index >= len(s) {
+return 0
+}
+
+if v := s[index]; v == '-' || v == '+' {
+if v == '-' {
+sign = -1
+}
+
+index++
+}
+
+for {
+if index == len(s) {
+break
+}
+
+if isNumericRune(s[index]) == false {
+return sign * val
+}
+
+val = val*10 + int(s[index]) - '0'
+
+if val > 2147483647 || val < -2147483648 {
+if sign == 1 {
+return 2147483647
+}
+
+return -2147483648
+}
+
+index++
+}
+
+return sign * val
+}
+
+func isNumericRune(x byte) bool {
+return x >= '0' && x <= '9'
+}

StringToInteger/string_to_integer.md

@@ -0,0 +1,132 @@
+
+# 🔥 String To Integer (Atoi) 🔥|| Simple Fast and Easy || with Explanation
+
+Converts a string to an integer, mimicking the behavior of the C `atoi` function.
+
+**Explanation:**
+
+1. **Whitespace Removal:**
+ * The input string `s` is stripped of leading and trailing whitespace using `s.strip()`.
+2. **Empty String Check:**
+ * If the stripped string is empty, the function returns 0.
+3. **Sign Determination:**
+ * The code checks the first character of the string for a sign (`'+'` or `'-'`).
+ * If a `'-'` is found, the `sign` variable is set to -1; otherwise, it defaults to 1.
+ * The `index` is incremented to move past the sign character.
+4. **Digit Extraction and Conversion:**
+ * The code iterates through the remaining characters of the string as long as they are digits.
+ * For each digit, it converts the character to its integer equivalent using `int(s[index])` and adds it to the `val` variable.
+ * The `val` variable is multiplied by 10 in each iteration to construct the integer.
+5. **Overflow Handling:**
+ * During the integer construction, the code checks if `val` exceeds the 32-bit signed integer range (`[-2147483648, 2147483647]`).
+ * If an overflow occurs:
+ * If the `sign` is positive, it returns `2147483647`.
+ * If the `sign` is negative, it returns `-2147483648`.
+6. **Return Value:**
+ * Finally, the function returns the calculated integer value (`sign * val`).
+
+## **Code:**
+
+```python
+class Solution:
+ def myAtoi(self, s: str) -> int:
+ s = s.strip()
+ if not s:
+ return 0
+
+ sign = 1
+ index = 0
+ val = 0
+
+ if s[0] == '-':
+ sign = -1
+ index += 1
+ elif s[0] == '+':
+ index += 1
+
+ while index < len(s) and s[index].isdigit():
+ val = val * 10 + int(s[index])
+ if val > 2147483647 or val < -2147483648:
+ if sign == 1:
+ return 2147483647
+ else:
+ return -2147483648
+ index += 1
+
+ return sign * val
+```
+
+
+## **Code - Golang**
+
+```go
+func myAtoi(s string) int {
+if len(s) == 0 {
+return 0
+}
+
+sign := 1 // -1 negative
+index := 0
+val := 0
+
+for len(s) > index && s[index] == ' ' {
+index++
+}
+
+if index >= len(s) {
+return 0
+}
+
+if v := s[index]; v == '-' || v == '+' {
+if v == '-' {
+sign = -1
+}
+
+index++
+}
+
+for {
+if index == len(s) {
+break
+}
+
+if isNumericRune(s[index]) == false {
+return sign * val
+}
+
+val = val*10 + int(s[index]) - '0'
+
+if val > 2147483647 || val < -2147483648 {
+if sign == 1 {
+return 2147483647
+}
+
+return -2147483648
+}
+
+index++
+}
+
+return sign * val
+}
+
+func isNumericRune(x byte) bool {
+return x >= '0' && x <= '9'
+}
+
+```
+
+
+## Space and Time Complexity
+
+**Time Complexity:**
+
+* **O(n)**, where `n` is the length of the input string `s`.
+ * The `strip()` operation takes O(n) time in the worst case.
+ * The `while` loop iterates through the string at most once.
+
+**Space Complexity:**
+
+* **O(1)** (constant).
+ * The code uses a fixed number of variables (`sign`, `index`, `val`), regardless of the input string's size.
+ * The `strip()` operation in python generally returns a new string, but in the case of no leading or trailing white space, it will return the same string. Therefore the space complexity remains constant.

StringToInteger/string_to_integer.py

@@ -0,0 +1,29 @@
+class Solution:
+ def myAtoi(self, s: str) -> int:
+
+ s = s.strip() 
+ if not s:
+ return 0
+
+ sign = 1
+ index = 0
+ val = 0
+
+ if s[0] == "-":
+ sign = -1
+ index += 1
+ elif s[0] == "+":
+ index += 1
+
+ while index < len(s) and s[index].isdigit():
+ val = val * 10 + int(s[index])
+
+ if val > 2147483647 or val < -2147483648:
+ if sign == 1:
+ return 2147483647
+ else:
+ return -2147483648
+
+ index += 1
+
+ return sign * val