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Copy path0053-Maximum-Subarray.cpp
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executable file
·53 lines (47 loc) · 1.39 KB
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/**
* Given an integer array nums, find the contiguous subarray (containing at least one number) which
* has the largest sum and return its sum.
*
* Example:
* Input: [-2,1,-3,4,-1,2,1,-5,4],
* Output: 6
* Explanation: [4,-1,2,1] has the largest sum = 6.
*
* Follow up: If you have figured out the O(n) solution, try coding another solution using the
* divide and conquer approach, which is more subtle.
*/
#include <iostream>
#include <vector>
using std::vector;
class Solution {
public:
int maxSubArray(vector<int>& nums) {
if (nums.empty()) return 0;
int sum = 0, max = nums[0], i = 0;
// if the leading contiguous numbers are negative, find the max one
for (; i < nums.size(); ++i) {
if (nums[i] > 0) break;
max = max > nums[i] ? max : nums[i];
}
// contains positive number, discard negative sum and restart from positive one
for (; i < nums.size(); ++i) {
sum += nums[i];
if (sum < 0) sum = 0;
else max = sum > max ? sum : max;
}
return max;
}
};
int main() {
Solution s;
int testId = 1;
vector<vector<int>> inputs{
{-2, 1, -3, 4, -1, 2, 1, -5, 4},
{-1},
{-2, -1}
};
for (auto &nums : inputs) {
auto res = s.maxSubArray(nums);
std::cout << "Case " << testId++ << ": " << res << std::endl;
}
}