525. Contiguous Array
Description
Difficulty: Medium
Related Topics: Array, Hash Table, Prefix Sum
Given a binary array nums, return the maximum length of a contiguous subarray with an equal number of 0 and 1.
Example 1:
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| Input: nums = [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with an equal number of 0 and 1.
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Example 2:
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| Input: nums = [0,1,0]
Output: 2
Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.
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Constraints:
- 1 <= nums.length <= 105
nums[i] is either 0 or 1.
Hints/Notes
- change 0 to -1 and make the range sum to be 0
Solution
Language: C++
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| class Solution {
public:
int findMaxLength(vector<int>& nums) {
int size = nums.size();
vector<int> preSum(size + 1, 0);
for (int i = 0; i < size; i++) {
preSum[i + 1] = preSum[i] + (nums[i] == 1 ? 1 : -1);
}
map<int, int> m;
int res = 0;
for (int i = 0; i <= size; i++) {
if (!m.count(preSum[i])) {
m[preSum[i]] = i;
} else {
res = max(res, i - m[preSum[i]]);
}
}
return res;
}
};
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