# 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.

``````class Solution {
public:
int findMaxLength(vector<int>& nums) {
int res = 0, n = nums.size(), sum = 0;
unordered_map<int, int> m{{0, -1}};
for (int i = 0; i < n; ++i) {
sum += (nums[i] == 1) ? 1 : -1;
if (m.count(sum)) {
res = max(res, i - m[sum]);
} else {
m[sum] = i;
}
}
return res;
}
};
``````

``````class Solution {
public:
int findMaxLength(vector<int>& nums) {
int res = 0, n = nums.size(), sum = 0;
unordered_map<int, int> m{{0, -1}};
for (int i = 0; i < n; ++i) {
sum += (nums[i] << 1) -1;
if (m.count(sum)) {
res = max(res, i - m[sum]);
} else {
m[sum] = i;
}
}
return res;
}
};
``````

Github 同步地址：

https://github.com/grandyang/leetcode/issues/525

https://leetcode.com/problems/contiguous-array/

https://leetcode.com/problems/contiguous-array/discuss/99646/Easy-Java-O(n)-Solution-PreSum-%2B-HashMap

https://leetcode.com/problems/contiguous-array/discuss/99652/One-passuse-a-HashMap-to-record-0-1-count-difference

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