LeetCode - Array - Maximum Subarray

最新推荐文章于 2022-01-26 01:33:09 发布

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本文介绍了一种算法来找到给定数组中具有最大和的连续子数组，包括一个具体的例子和两种不同的实现方式。

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array [−2,1,−3,4,−1,2,1,−5,4],

the contiguous subarray [4,−1,2,1] has the largest sum = 6.

class Solution {
public:
    int maxSubArray(int A[], int n) {
        if(A==NULL)
            return 0;
        int result=INT_MIN,temp=0;
        for(int i=0;i<n;i++)
        {
            temp+=A[i];
            result=max(temp,result);
            if(temp<0)
                temp=0;
        }
        return result;
    }
};

class Solution {
public:
    int maxSubArray(int A[], int n) {
        if(A==NULL)
            return 0;
        maxSub(A, 0, n-1);
        
    }
    int maxSub(int A[], int b, int e)
    {
        if(b==e)
            return A[b];
        if(b+1==e)
            return max(max(A[b],A[e]),A[b]+A[e]);
        int mid=(b+e)/2;
        int maxLeft=maxSub(A, b, mid-1);
        int maxRight=maxSub(A,mid+1,e);
        int maxMid;
        int maxMidLeft=INT_MIN,maxMidRight=INT_MIN;
        int maxTemp1=0,maxTemp2=0;
        for(int i=mid;i>=0;i--)
        {
            maxTemp1+=A[i];
            maxMidLeft=max(maxMidLeft,maxTemp1);
        }
        for(int i=mid;i<=e;i++)
        {
            maxTemp2+=A[i];
            maxMidRight=max(maxMidRight, maxTemp2);
        }
        maxMid=maxMidRight+maxMidLeft-A[mid];
        return max(max(maxLeft,maxMid),maxRight);
    }
};