最大子序和

最大连续子数组

53. 最大子序和 - 力扣（LeetCode） (leetcode-cn.com)

我的做法，用前缀和

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        int * presum = new int[nums.size()];
        
        for (int i = 0; i < nums.size(); i++)
            presum[i] = nums.at(i) + (i == 0 ? 0 :presum[i - 1]);
        
        int min = 0;
        int max = presum[0];
        for (int i = 0; i < nums.size(); i++)
        {
            if (presum[i] - min > max)
                max = presum[i] - min;
            if (presum[i] < min)
                min = presum[i];
            
        }
        delete []presum;
        return max;
    }
};

官方题解

动态规划

pre = max(pre+x, x);

maxAns = max(maxAns, pre);

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        int maxAns = nums.at(0);
        int pre = 0;
        for (int x : nums)
        {
            pre = max(pre + x, x);
            maxAns = max(maxAns, pre);
        }
        return maxAns;
    }
};