Problem

Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.

example 1

Input: [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with equal number of 0 and 1.

example 2

Input: [0,1,0]
Output: 2
Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.

Constraints

• The length of the given binary array will not exceed 50,000.

Solution

1. init sum
2. walk throw givven array ,and sum++ if current elemen(nums[idx]) equeal 1, and sum-- if current element equal -1
3. if in map exist elemant with key sum, compare idx-m[sum]+1 and max; if max if less – set max=idx-m[sum]+1
4. Set to map m[sum] = idx+1

func findMaxLength(nums []int) int {
    max := 0
    m := make(map[int]int, 0)
    s:=0
    m[0]=0
    for idx:=range nums {
        if nums[idx] == 1{
            s+=1
        } else {
            s-=1
        }
        _, ok := m[s]
        if ok {
            if idx-m[s]+1>max {
                max = idx-m[s]+1
            }
        } else {
            m[s] = idx+1
        }
        
    }
    
    return max
}