leetcode53
1.dp动态规划
class Solution {
public:int maxSubArray(vector<int>& nums) {int len=nums.size();if(len==0) return 0;if(len==1) return nums[0];vector<int>dp(len,0);dp[0]=nums[0];int max_num=dp[0];int i=1;for(;i!=len;++i){if(dp[i-1]>0)dp[i]=dp[i-1]+nums[i];elsedp[i]=nums[i];max_num=max(dp[i],max_num);}return max_num;}
};
2.分治，没太懂
class Solution {
public:int maxSubArray(vector<int>& nums) {if(!nums.size()) return 0;return helper(nums,0,nums.size()-1);}int helper(vector<int>&nums,int l,int r){if(l>r) return INT_MIN;if(l==r) return nums[l];int mid=(l+r)/2;int left=helper(nums,l,mid-1);int right=helper(nums,mid+1,r);int t=nums[mid];int max_num=nums[mid];for(int i=mid-1;i>=0;i--){t+=nums[i];max_num=max(max_num,t);}t=max_num;for(int i=mid+1;i<=r;i++){t+=nums[i];max_num=max(max_num,t);}return max(max(left,right),max_num);}
};
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