LeetCode_416_分割等和子集

二维dp数组

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        //sort(nums.begin(), nums.end()); 并不需要排序
        int sum = 0;
        for (int i = 0; i < nums.size(); i++) {
            sum += nums[i];
        }
        if (sum % 2 != 0) return false;
        int bagweight = sum / 2;
        vector<vector<int> > dp(nums.size(), vector<int>(bagweight + 1, 0));
        for (int j = nums[0]; j <= bagweight; j++) {
            dp[0][j] = nums[0];
        }
        for (int i = 1; i < nums.size(); i++) {
            for (int j = 0; j <= bagweight; j++) {
                if (j < nums[i]) dp[i][j] = dp[i - 1][j];
                else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - nums[i]] + nums[i]);
            }
        }
        if (dp[nums.size() - 1][bagweight] == bagweight) return true;
        return false;
    }
};

一维dp数组

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        int sum = 0;
        for (int i = 0; i < nums.size(); i++) {
            sum += nums[i];
        }
        if (sum % 2 != 0) return false;
        int bagweight = sum / 2;
        vector<int> dp(bagweight + 1, 0);
        for (int j = nums[0]; j <= bagweight; j++) {
            dp[j] = nums[0];
        }
        for (int i = 1; i < nums.size(); i++) {
            for (int j = bagweight; j >= nums[i]; j--) {
                dp[j] = max(dp[j], dp[j - nums[i]] + nums[i]);
            }
        }
        if (dp[bagweight] == bagweight) return true;
        return false;
    }
};