最大子数组和(cpp)

1.暴力求解法

class Solution {
public:
    int maxSubArray(vector& nums) {
        int n = nums.size();
        int ans = INT_MIN;
        for (int i = 0; i < n; i++){
            for (int j = i; j < n; j++){
                int sum = 0;
                for (int k = i; k <= j; k++){
                    sum += nums[k];
                }
                if(sum > ans){
                    ans = sum;
                }
            }
        }
        return ans;
    }
};

2.优化枚举（动态规划）法

class Solution {
public:
    int maxSubArray(vector& nums) {
        int n = nums.size();
        int ans = INT_MIN;
        for (int i = 0; i < n; i++){
            int sum = 0;
            for (int j = i; j < n; j++){
                sum += nums[j];
                if(sum > ans){
                    ans = sum;
                }
            }
        }
        return ans;
    }
};

3.贪心法

class Solution {
public:
    int maxSubArray(vector& nums) {
        int n = nums.size();
        int ans = INT_MIN;
        int sum = 0;
        for (int i = 0; i < n; i++){
            sum += nums[i];
            if(sum > ans){
                ans = sum;
            }
            if (sum < 0){
                sum = 0;
            }
        }
        return ans;
    }
};

4.分治法