97 lines
2.7 KiB
C++
97 lines
2.7 KiB
C++
// Source : https://leetcode.com/problems/maximum-absolute-sum-of-any-subarray/
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// Author : Hao Chen
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// Date : 2021-02-12
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/*****************************************************************************************************
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*
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* You are given an integer array nums. The absolute sum of a subarray [numsl, numsl+1, ..., numsr-1,
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* numsr] is abs(numsl + numsl+1 + ... + numsr-1 + numsr).
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*
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* Return the maximum absolute sum of any (possibly empty) subarray of nums.
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*
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* Note that abs(x) is defined as follows:
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*
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* If x is a negative integer, then abs(x) = -x.
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* If x is a non-negative integer, then abs(x) = x.
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*
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* Example 1:
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*
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* Input: nums = [1,-3,2,3,-4]
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* Output: 5
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* Explanation: The subarray [2,3] has absolute sum = abs(2+3) = abs(5) = 5.
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*
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* Example 2:
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*
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* Input: nums = [2,-5,1,-4,3,-2]
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* Output: 8
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* Explanation: The subarray [-5,1,-4] has absolute sum = abs(-5+1-4) = abs(-8) = 8.
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*
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* Constraints:
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*
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* 1 <= nums.length <= 105
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* -104 <= nums[i] <= 104
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******************************************************************************************************/
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class Solution {
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public:
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int maxAbsoluteSum(vector<int>& nums) {
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return maxAbsoluteSum02(nums); //56ms
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return maxAbsoluteSum01(nums); //56ms
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}
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int maxAbsoluteSum01(vector<int>& nums) {
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return std::max(maxSumArray(nums), std::abs(minSumArray(nums)) );
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}
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//https://en.wikipedia.org/wiki/Maximum_subarray_problem
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int maxSumArray(vector<int>& nums) {
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int max = nums[0];
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int sum = nums[0];
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for (int i = 1; i < nums.size(); i++) {
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if (sum < 0 ) sum = nums[i];
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else sum += nums[i];
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if (max < sum) max = sum;
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}
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return max;
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}
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int minSumArray(vector<int>& nums) {
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int min = nums[0];
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int sum = nums[0];
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for (int i = 1; i < nums.size(); i++) {
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if (sum > 0 ) sum = nums[i];
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else sum += nums[i];
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if (min > sum) min = sum;
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}
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return min;
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}
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// Becasue maxSumArray() & minSumArray() are two similar,
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// we can merge them together to save one loop
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int maxAbsoluteSum02(vector<int>& nums) {
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int max = nums[0];
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int max_sum = nums[0];
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int min = nums[0];
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int min_sum = nums[0];
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for (int i = 1; i < nums.size(); i++) {
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if (max_sum < 0 ) max_sum = nums[i];
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else max_sum += nums[i];
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if (max < max_sum) max = max_sum;
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if (min_sum > 0 ) min_sum = nums[i];
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else min_sum += nums[i];
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if (min > min_sum) min = min_sum;
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}
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return std::max(max, abs(min));
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}
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};
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