Leetcode Hot100 第30题 416.分割等和子集

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        int sum=0;
        for(int num:nums){
            sum+=num;
        }
        if(sum%2==1) return false;
        int bag_size = sum/2;
        // return dfs(nums,nums.size()-1,bag_size);//递归做法
        vector<vector<bool>> dp(nums.size()+1,vector<bool>(bag_size+1));
        dp[0][0]=true;
        for(int i=1;i<=nums.size();i++){
            for(int j=0;j<=bag_size;j++){
                if(j-nums[i-1]<0) dp[i][j] = dp[i-1][j];
                else dp[i][j] = dp[i-1][j]||dp[i-1][j-nums[i-1]];
            }
        }
        return dp[nums.size()][bag_size];
    }

    bool dfs(vector<int>& nums, int i, int target){
        if(i<0) return target==0? true: false;
        if(target==0) return true;
        if(target<0) return false;
        return dfs(nums,i-1,target-nums[i])||dfs(nums,i-1,target);
    }
};