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[Swift]LeetCode29. 两数相除 | Divide Two Integers

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➤微信公众号：山青咏芝（shanqingyongzhi）
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➤原文地址：https://www.cnblogs.com/strengthen/p/9894980.html
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Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.

Return the quotient after dividing dividend by divisor.

The integer division should truncate toward zero.

Example 1:

Input: dividend = 10, divisor = 3
Output: 3

Example 2:

Input: dividend = 7, divisor = -3
Output: -2

Note:

Both dividend and divisor will be 32-bit signed integers.
The divisor will never be 0.
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2^31, 2^31 − 1]. For the purpose of this problem, assume that your function returns 2^31 − 1 when the division result overflows.

给定两个整数，被除数 dividend 和除数 divisor。将两数相除，要求不使用乘法、除法和 mod 运算符。

返回被除数 dividend 除以除数 divisor 得到的商。

示例 1:

输入: dividend = 10, divisor = 3
输出: 3

示例 2:

输入: dividend = 7, divisor = -3
输出: -2

说明:

被除数和除数均为 32 位有符号整数。
除数不为 0。
假设我们的环境只能存储 32 位有符号整数，其数值范围是 [−2^31, 2^31 − 1]。本题中，如果除法结果溢出，则返回 2^31 − 1。

8ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         if divisor == Int32.min {
 4             return dividend == Int32.min ? 1 : 0    
 5         }
 6         var dividend = dividend
 7         var divisor = divisor
 8         var hasSign = (dividend < 0 && divisor > 0) || (dividend > 0 && divisor < 0)
 9         var extra = 0
10         if dividend == Int32.min {
11             if divisor == -1 {
12                 return Int(Int32.max)
13             } else if divisor > 0 {
14                 dividend += divisor
15             } else {
16                 dividend -= divisor
17             }
18             extra += 1
19         }
20         
21         
22         let result = dividePositive(abs(dividend), abs(divisor)) + extra
23         return hasSign ? -result : result
24     }
25     
26     func dividePositive(_ dividend: Int, _ divisor: Int) -> Int {
27         var first = dividend
28         var second = divisor
29         var power = 0
30         var result = 0
31         
32         while (first - second >= second) {
33             second <<= 1
34             power += 1
35         }
36         
37         while first >= second {
38             result += (1 << power)
39             first -= second
40             while power > 0 && first < second {
41                 power -= 1
42                 second >>= 1
43             }
44         }
45         return result
46     }
47 }

16ms

 1 class Solution {
 2      func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         var quocient : Int = 0
 4         var currentDivident = abs(dividend)
 5         let currentDivisor = abs(divisor)
 6         
 7         if currentDivisor == 1 {
 8             if divisor < 0 {
 9                 currentDivident *= -1
10             }
11             if dividend < 0 {
12                 currentDivident *= -1
13             }
14             currentDivident = analiseLimits(quocient: currentDivident)
15             return currentDivident
16         }
17         
18         var iCount = 0
19         
20         for i in 1...currentDivident {
21             if (currentDivident - currentDivisor * i) >= 0 {
22                 quocient += i
23                 iCount = i
24                 currentDivident -= currentDivisor * i
25             } else {
26                 break
27             }
28         }
29         
30         while currentDivident >= currentDivisor {
31             while currentDivident >= currentDivisor * iCount {
32                 quocient += iCount
33                 currentDivident -= currentDivisor * iCount
34             }
35             iCount -= 1
36             if iCount == 0 {
37                 break
38             }
39         }
40         
41         
42         quocient = invert(quocient: quocient, dividend: dividend, divisor: divisor)
43         quocient = analiseLimits(quocient: quocient)
44         
45         return quocient
46     }
47     
48     func invert(quocient: Int, dividend: Int, divisor: Int) -> Int {
49         var newQuocient = quocient
50         if dividend < 0 {
51             newQuocient *= -1
52         }
53         if divisor < 0{
54             newQuocient *= -1
55         }
56         return newQuocient
57     }
58     
59     func analiseLimits(quocient: Int) -> Int {
60         var newQuocient = quocient
61         if quocient > 2147483647 {
62             print(quocient)
63             newQuocient = 2147483647
64         } else if quocient < -2147483648 {
65             newQuocient = -2147483648
66         }
67         return newQuocient
68     }
69 }

20ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         if divisor == 0 {
 4             return Int.max - 1
 5         }
 6         
 7         let isNegative = (dividend < 0) != (divisor < 0)
 8         var dividend = abs(dividend)
 9         var divisor = abs(divisor)
10         var count = 0
11         
12         while dividend >= divisor {
13             var shift = 0
14             
15             while dividend >= (divisor << shift) {
16                 shift += 1
17             }
18             
19             dividend -= divisor << (shift - 1)
20             count += 1 << (shift - 1)
21         }
22         if count >= 2147483648 && !isNegative{
23             return 2147483647
24         }
25         return isNegative ? -count : count
26     }
27 }

20ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         let isNegative = (dividend > 0 && divisor < 0) || (dividend < 0 && divisor > 0)
 4         guard dividend != divisor else { return 1 }
 5         guard dividend != 0 else { return 0 }
 6         var y = abs(divisor)
 7         var x = abs(dividend)
 8         if dividend == Int(Int32.max), y == 1 {
 9             return isNegative ? -Int(Int32.max) : dividend
10         }
11         if dividend == Int(Int32.min), y == 1 {
12             return isNegative ? Int(Int32.min) : Int(Int32.max)
13         }
14         guard y != x else { return -1 }
15         var count = 0
16         while (x > y) {
17             var i = 1
18             var j = 0
19             while (x >= y << 1) {
20                 y = y << 1
21                 i = i << 1
22                 j += 1
23             }
24             x -= y
25             y = y >> j
26             count += i
27         }
28         return isNegative ? -count : count
29     }
30 }

20ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         if dividend == -2147483648 && divisor == -1 {return 2147483647}
 4         var flag:Int = 1,ans:Int = 0
 5         if dividend == 0 {return 0}
 6         else if divisor == 1 {return dividend}
 7         else if divisor == -1 {return -dividend}
 8         
 9         var long_dividend:Int64 = Int64(dividend)
10         var long_divisor:Int64 = Int64(divisor)
11         
12         if long_dividend < 0 && divisor < 0
13         {
14             long_dividend = -long_dividend
15             long_divisor = -long_divisor
16         }
17         else if long_dividend < 0 || long_divisor < 0
18         {
19             flag = -1
20             long_dividend = abs(long_dividend)
21             long_divisor = abs(long_divisor)
22         }
23         
24         if long_dividend < long_divisor {return 0}
25         var k:Int = 1
26         var tmp:Int64 = long_divisor
27         while (tmp << 1 < long_dividend && tmp << 1 > 0)
28         {
29             tmp <<= 1
30             k <<= 1
31         }
32         ans += k
33         long_dividend -= tmp
34         
35         while (long_dividend >= long_divisor)
36         {
37             while (tmp > long_dividend)
38             {
39                 k >>= 1
40                 tmp >>= 1
41             }
42             long_dividend -= tmp
43             ans += k
44         }
45         return flag * ans
46     }
47 }

24ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         let sign: Int64 = (dividend > 0 && divisor > 0) || (dividend < 0 && divisor < 0) ? 1 : -1
 4         let lDividend = dividend < 0 ? -Int64(dividend) : Int64(dividend)
 5         let lDivisor = divisor < 0 ? -Int64(divisor) : Int64(divisor)
 6         var result: Int64 = 0
 7         var left: Int64 = 1
 8         var right: Int64 = lDividend
 9         var middle: Int64 = 0
10         
11         while left <= right {
12             middle = (left + right) / 2
13             if middle * lDivisor <= lDividend {
14                 result = middle
15                 left = middle + 1
16             } else {
17                 right = middle - 1
18             }
19         }
20         
21             if Int(result * sign) >= 2147483648 {
22                 return 2147483647
23             } else {
24                 return Int(result * sign)
25             }
26     }
27 }

24ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         if dividend == 0{
 4             return 0;
 5         }
 6         var isNeed = false
 7         var dividend = dividend;
 8         var divisor = divisor;
 9         if dividend > 0 && divisor < 0{
10             isNeed = true
11             divisor = 0 - divisor;
12         }else if dividend < 0 && divisor > 0{
13             isNeed = true
14             dividend = 0 - dividend;
15         }else if dividend < 0 && divisor < 0{
16             divisor = 0 - divisor;
17             dividend = 0 - dividend;
18         }
19         if divisor == 1{
20             
21             if isNeed {
22                 return Int(Int32(0 - dividend));
23             }else{
24                 if dividend >= 2^31{
25                     return Int(Int32.max)
26                 }
27                 return Int(Int32(dividend));
28             }
29         }
30         var i = 0;
31         while divisor <= dividend {
32             var temp = divisor;
33             var cnt = 1;
34             while dividend >= temp{
35                 temp = temp<<1
36                 cnt = cnt<<1
37             }
38             i += (cnt>>1)
39             dividend -= (temp>>1)
40         }
41         if isNeed {
42             return Int(0 - i);
43         }else{
44             return Int(i);
45         }
46     }
47 }

28ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         if divisor == 0 || (dividend == -Int(INT32_MAX) - 1 && divisor == -1) {
 4             return Int(INT32_MAX)
 5         }
 6         
 7         var a = abs(dividend), b = abs(divisor), res = 0
 8         let sign = (dividend > 0 && divisor > 0 || dividend < 0 && divisor < 0) ? 1 : -1
 9         if b == 1 {
10             return a * sign
11         }
12         
13         
14         while a >= b {
15             var m = b, n = 1
16             while (a >= (m << 1)) {
17                 m <<= 1
18                 n <<= 1
19             }
20             res += n
21             a -= m
22         }
23         
24         return res * sign
25     }
26 }

32ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         
 4         guard dividend != 0 else {
 5             return 0
 6         }
 7         
 8         guard divisor != 0 else {
 9             return Int(Int32.max)
10         }
11         
12         guard divisor != 1 else {
13             return dividend
14         }
15         
16         guard divisor != -1 else {
17             if dividend == Int32.min {
18                 return Int(Int32.max)
19             }
20             
21             return dividend * -1
22         }
23         
24         let isNegative = ((dividend < 0 && divisor > 0) || (dividend > 0 && divisor < 0))
25         
26         var tmpDividend = abs(dividend)
27         let tmpDivisor = abs(divisor)
28         var result = 0
29         var fac = 1
30         var incDivisor = tmpDivisor
31         
32         while tmpDividend >= tmpDivisor {
33             if tmpDividend < incDivisor {
34                 incDivisor = tmpDivisor
35                 fac = 1
36             }
37             
38             tmpDividend -= incDivisor
39             
40             result += fac
41             
42             incDivisor += incDivisor
43             fac += fac
44         }
45         
46         return isNegative ? result * -1 : result
47     }
48 }

44ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         
 4         /// 被除数为0，结果肯定是0
 5         guard dividend != 0 else {
 6             return 0
 7         }
 8         
 9         /// 除数为0，返回32位最大值
10         guard divisor != 0 else {
11             return Int(Int32.max)
12         }
13         
14         /// 除数为1，直接返回
15         guard divisor != 1 else {
16             return dividend
17         }
18         
19         /// 除数为-1
20         guard divisor != -1 else {
21             /// 被除数为-1，结果会越界，则返回32位最大值
22             if dividend == Int32.min {
23                 return Int(Int32.max)
24             }
25             
26             /// 直接取反
27             return dividend * -1
28         }
29         
30         /// 记录一下是否是负数
31         let isNegative = ((dividend < 0 && divisor > 0) || (dividend > 0 && divisor < 0))
32         
33         var tmpDividend = abs(dividend)     // 取正数，方便计算
34         let tmpDivisor = abs(divisor)       // 取正数，方便计算
35         var result = 0                      // 商，结果
36         var fac = 1                         // 除数的倍数，指数式的增长，减小循环的次数
37         var incDivisor = tmpDivisor         // 真正用来作为减数的数
38         
39         // 只有在被除数大于除数的时候才能进入循环
40         while tmpDividend >= tmpDivisor {
41             // 当被除数比减数还小，那么重置减数
42             if tmpDividend < incDivisor {
43                 incDivisor = tmpDivisor
44                 fac = 1
45             }
46             
47             // 减去减数
48             tmpDividend -= incDivisor
49             
50             // 对商进行累加
51             result += fac
52             
53             // 指数式的增长减数
54             incDivisor += incDivisor
55             fac += fac
56         }
57         
58         return isNegative ? result * -1 : result
59     }
60 }

48ms

 1 class Solution {
 2     func divide(_ dividend: Int, _ divisor: Int) -> Int {
 3         let div = dividend < 0 ? -dividend : dividend
 4         let dsr = divisor < 0 ? -divisor : divisor
 5         
 6         guard div >= dsr else {
 7             return 0
 8         }
 9         
10         var lfmove = 1
11         while (dsr<<lfmove) < div  {
12             lfmove += 1
13         }
14         
15         var res = 1<<lfmove
16         var sum = dsr<<lfmove
17         while lfmove > 0 {
18             lfmove -= 1
19             if sum > div {
20                 sum -= (dsr<<lfmove)
21                 res -= (1<<lfmove)
22             }
23             else {
24                 sum += (dsr<<lfmove)
25                 res += (1<<lfmove)
26             }
27         }
28         
29         res = sum > div ? res - 1 : res
30         res = (dividend > 0 && divisor > 0) || (dividend < 0 && divisor < 0) ? res : -res
31         res = res > Int32.max ? Int(Int32.max) : res
32         res = res < Int32.min ? Int(Int32.min) : res
33        
34         return res
35     }
36 }

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原文地址：https://www.cnblogs.com/strengthen/p/9894980.html