Minimum Number of Increments on Subarrays to Form a Target Array LeetCode solution in Java

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// Imagine 3 cases
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// Case 1. [3,2,1], we need 3 operations.
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// Case 2. [1,2,3], we need 3 operations.
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// Case 3. [3,2,1,2,3], we need 5 operations.
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// What we need to add is actually the diff (cur - prev)
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// Time complexity: O(N)
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// Space complexity: O(1)
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class Solution {
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  public int minNumberOperations(int[] target) {
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    int res = 0;
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    int prev = 0;
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    for (int cur : target) {
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      if (cur > prev) {
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        res += cur - prev;
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      }
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      prev = cur;
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    }
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    return res;
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  }
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}