525. Contiguous Array

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.
```

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

525. Contiguous Array
``````struct Solution;

use std::collections::HashMap;

impl Solution {
fn find_max_length(nums: Vec<i32>) -> i32 {
let mut res: usize = 0;
let mut hm: HashMap<i32, usize> = HashMap::new();
let mut diff = 0;
let n = nums.len();
hm.entry(0).or_default();
for i in 0..n {
if nums[i] == 1 {
diff += 1;
} else {
diff -= 1;
}
let j = *hm.entry(diff).or_insert(i + 1);
res = usize::max(i + 1 - j, res);
}
res as i32
}
}

#[test]
fn test() {
let nums = vec![0, 1];
let res = 2;
assert_eq!(Solution::find_max_length(nums), res);
let nums = vec![0, 1, 0];
let res = 2;
assert_eq!(Solution::find_max_length(nums), res);
}
``````