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➤微信公众号：山青咏芝（shanqingyongzhi）
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Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.
Example:
Given a = 1 and b = 2, return 3.
Credits:
Special thanks to @fujiaozhu for adding this problem and creating all test cases.
不使用运算符 + 和 - ，计算两整数 a 、b 之和。
示例 1:
输入: a = 1, b = 2 输出: 3
示例 2:
输入: a = -2, b = 3 输出: 1
8ms
1 class Solution { 2 func getSum(_ a: Int, _ b: Int) -> Int { 3 //按位取异或 4 var res:Int = a^b 5 //判断是否需要进位 6 var forward = (a&b) << 1 7 if forward != 0 8 { 9 //如有进位，则将二进制数左移一位，进行递归 10 return getSum(res, forward) 11 } 12 return res 13 } 14 }
8ms
1 class Solution { 2 func getSum(_ a: Int, _ b: Int) -> Int { 3 if a == 0 { 4 return b 5 } 6 7 if b == 0 { 8 return a 9 } 10 11 var a = a 12 var b = b 13 while b != 0 { 14 let carry = a & b 15 a = a ^ b 16 b = carry << 1 17 } 18 return a 19 } 20 }
8ms
1 class Solution { 2 func getSum(_ a: Int, _ b: Int) -> Int { 3 if a&b==0 { 4 return a|b 5 } 6 return getSum(a^b, (a&b)<<1) 7 } 8 }
12ms
1 class Solution { 2 func getSum(_ a: Int, _ b: Int) -> Int { 3 var carry = (a & b) << 1 4 var result = a ^ b 5 while carry != 0 { 6 let carryTemp = carry 7 carry = (result & carryTemp) << 1 8 result = result ^ carryTemp 9 } 10 return result 11 } 12 }
16ms
1 class Solution { 2 func getSum(_ a: Int, _ b: Int) -> Int { 3 4 if b == 0 { 5 return a 6 } else { 7 return getSum(a ^ b, (a & b) << 1) 8 } 9 } 10 }