连续数组

给定一个二进制数组 nums , 找到含有相同数量的 0 和 1 的最长连续子数组，并返回该子数组的长度。

/**
 * @param {number[]} nums
 * @return {number}
 */
const findMaxLength = (nums) => {
    let maxLength = 0;
    const map = new Map();
    let counter = 0;
    map.set(counter, -1);
    const n = nums.length;
    for (let i = 0; i < n; i++) {
        const num = nums[i];
        if (num == 1) {
            counter++;
        } else {
            counter--;
        }
        if (map.has(counter)) {
            const prevIndex = map.get(counter);
            maxLength = Math.max(maxLength, i - prevIndex);
        } else {
            map.set(counter, i);
        }
    }
    return maxLength;
};