Solved some of array & string problem from top 150 interview Questions.

Author: jyotisirswa

DataStrucutureQuestions/Array/134. Gas Station.playground/Contents.swift

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+import UIKit
+
+//https://leetcode.com/problems/gas-station/?envType=study-plan-v2&envId=top-interview-150
+
+func canCompleteCircuit(_ gas: [Int], _ cost: [Int]) -> Int {
+     var result = 0
+     var total = 0
+     if  gas.reduce(0, +) < cost.reduce(0, +) {
+         return -1
+     }
+     for index in 0..<gas.count {
+         total += (gas[index] - cost[index])
+         if total < 0 {
+             total = 0
+             result = index + 1
+         }
+     }
+     return result
+}
+
+print("starting gas station's index is :- \(canCompleteCircuit([1,2,3,4,5], [3,4,5,1,2]))")
+print("starting gas station's index is :- \(canCompleteCircuit([2,3,4], [3,4,3]))")

DataStrucutureQuestions/Array/134. Gas Station.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/Array/68. Text Justification.playground/Contents.swift

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+import UIKit
+
+//https://leetcode.com/problems/text-justification/description/?envType=study-plan-v2&envId=top-interview-150
+
+func fullJustify(_ words: [String], _ maxWidth: Int) -> [String] {
+    var result : [String] = []
+    var line : [String]  = [], length = 0
+    var index = 0
+    
+    while index < words.count {
+        if length + line.count + words[index].count > maxWidth {
+            //Line Complete
+            
+            var extraSpace = maxWidth - length
+            
+            let spaces = extraSpace / max(1, line.count - 1)
+            var remainder = extraSpace % max(1, line.count - 1)
+            
+            for j in 0..<max(1, line.count - 1) {
+                line[j] +=  String(repeating: " ", count: spaces)
+                if remainder > 0 {
+                    line[j] += " "
+                    remainder -= 1
+                }
+            }
+            result.append(line.joined(separator: ""))
+            line = []
+            length = 0 //reset line & length
+        }
+        line.append(words[index])
+        length += words[index].count
+        index += 1
+    }
+    //Handling last line
+    var last_line = line.joined(separator: " ")
+    var trail_Space = maxWidth - last_line.count
+    
+    result.append(last_line + String(repeating: " ", count: trail_Space))
+    
+    return result
+}
+
+print(fullJustify(["This", "is", "an", "example", "of", "text", "justification."], 16))
+print(fullJustify(["What","must","be","acknowledgment","shall","be"], 16))
+print(fullJustify(["Science","is","what","we","understand","well","enough","to","explain","to","a","computer.","Art","is","everything","else","we","do"], 20))

DataStrucutureQuestions/Array/68. Text Justification.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/String/28. Find the Index of the First Occurrence in a String.playground/Contents.swift

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+import UIKit
+
+//https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/description/?envType=study-plan-v2&envId=top-interview-150
+
+func strStr(_ haystack: String, _ needle: String) -> Int {
+    let lengthOfHay = haystack.count, lengthOfN = needle.count
+    if lengthOfHay == 0 || haystack == needle { return 0 }
+    guard lengthOfHay >=  lengthOfN else { return -1 }
+    var indexInitialOfHay = haystack.startIndex
+    
+    for pointer in 0...(lengthOfHay - lengthOfN) {
+        var endIndex = haystack.index(indexInitialOfHay, offsetBy : lengthOfN)
+        if haystack[indexInitialOfHay..<endIndex] == needle { return pointer }
+        indexInitialOfHay = haystack.index(after: indexInitialOfHay)
+    }
+    return -1
+}
+
+print("Index of First occurance of sad in String sadbutsad is :-  \(strStr("sadbutsad", "sad"))")
+print("Index of First occurance of leeto in String leetcode is :- \(strStr("leetcode", "leeto"))")

DataStrucutureQuestions/String/28. Find the Index of the First Occurrence in a String.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

DataStrucutureQuestions/String/6. Zigzag Conversion.playground/Contents.swift

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+import UIKit
+
+//https://leetcode.com/problems/zigzag-conversion/description/?envType=study-plan-v2&envId=top-interview-150
+
+func convert(_ s: String, _ numRows: Int) -> String {
+    if numRows == 1 {
+        return s
+    }
+    var res = ""
+    let increment = 2 * (numRows - 1)
+    //print("increament = \(increment)")
+    for r in 0..<numRows {
+        var i = r
+        //print("in for loop i = \(i)")
+        //print("in for loop r = \(r)")
+        while i < s.count {
+            //print("in while loop i = \(i)")
+            res += String(s[s.index(s.startIndex, offsetBy: i)])
+            //print("in while loop res = \(res)")
+            if r > 0 && r < numRows - 1 && i + increment - 2 * r < s.count {
+                res += String(s[s.index(s.startIndex, offsetBy: i + increment - 2 * r)])
+                //print("in if condition res = \(res)")
+            }
+            i += increment
+        }
+    }
+    return res
+}
+
+print("ZigZag conversion of PAYPALISHIRING is :-  \(convert("PAYPALISHIRING", 3))")
+print("ZigZag conversion of PAYPALISHIRING is :-  \(convert("PAYPALISHIRING", 4))")

DataStrucutureQuestions/String/6. Zigzag Conversion.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>