int vs int32返回值

Question

I am running into an issue, which seems to be related to int32 vs int data type. My program is returning different values on different environments.

For example, on go playground, I notice the value returned is -4 (which is expected value). But the same on Leetcode with same input returns a value of 4294967292. While it returned this value, when I print it, I get -4 ( see output added later).

I tried casting to int32(res) but didn't help. Also didn't find any directly related in textbook. Please help me understand why this is different on playground vs lc.

https://play.golang.org/p/qXMd9frlhbe

package main

import (
    "fmt"
)

func main() {
    fmt.Printf("%v", singleNumber([]int{-2,-2,1,1,-3,1,-3,-3,-4,-2}))
}

func singleNumber(nums []int) int {
    sum := make([]int, 32)

    for _, v := range nums {
        for i := 0; i < 32; i++ {
            if sum[i] != 0 {
                sum[i] += 1 & (v >> uint32(i))
            } else {
                sum[i] = 1 & (v >> uint32(i))
            }
        }
    }

    res := 0 
    for k, v := range sum {
        if (v%3) != 0 {
            res |= (v%3) << uint32(k) 
        }
    }
    fmt.Printf("res %+v
", res)
    return res
}

Same on Leetcode gives the output:-

Input:
[-2,-2,1,1,-3,1,-3,-3,-4,-2]
Output:
4294967292
Expected:
-4
Stdout:
res -4

Answer 1

The textbook you are looking for is

The Go Programming Language Specification

Numeric types

A numeric type represents sets of integer or floating-point values. The predeclared architecture-independent numeric types are:

uint32 set of all unsigned 32-bit integers (0 to 4294967295)
uint64 set of all unsigned 64-bit integers (0 to 18446744073709551615)

int32  set of all signed 32-bit integers (-2147483648 to 2147483647)
int64  set of all signed 64-bit integers (-9223372036854775808 to 9223372036854775807)

There is also a set of predeclared numeric types with implementation-specific sizes:

uint either 32 or 64 bits
int  same size as uint

---

Check the size of type int. On the Go Playground it's 4 bytes or 32 bits.

package main

import (
    "fmt"
    "runtime"
    "unsafe"
)

func main() {
    fmt.Println("arch", runtime.GOARCH)
    fmt.Println("int", unsafe.Sizeof(int(0)))
}

Playground: https://play.golang.org/p/2A6ODvhb1Dx

Output (Playground):

arch amd64p32
int 4

Run the program in your (LeetCode) environment. It's likely 8 bytes or 64 bits.

For example, in my environment,

Output (Local):

arch amd64
int 8

---

Here are some fixes to your code,

package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Println(runtime.GOARCH)
    fmt.Printf("%v
", singleNumber([]int{-2, -2, 1, 1, -3, 1, -3, -3, -4, -2}))
}

func singleNumber(nums []int) int {
    sum := make([]int, 64)

    for _, v := range nums {
        for i := range sum {
            sum[i] += 1 & (v >> uint(i))
        }
    }

    res := 0
    for k, v := range sum {
        if (v % 3) != 0 {
            res |= (v % 3) << uint(k)
        }
    }
    fmt.Printf("res %+v
", res)
    return res
}

Playground: https://play.golang.org/p/kaoSuesu2Oj

Output (Playground):

amd64p32
res -4
-4

Output (Local):

amd64
res -4
-4