代码随想录算法训练营第31天 | 第九章 动态规划04

今日记录

1049.最后一块石头的重量II

Leetcode链接

class Solution {
public:
    int lastStoneWeightII(vector<int>& stones) {
        vector<int> dp(15001, 0);
        int sum = 0;
        for (int i = 0; i < stones.size(); i++) {
            sum += stones[i];
        }
        int target = sum / 2; // 向下取整
        for (int i = 0; i < stones.size(); i++) {
            for (int j = target; j >= stones[i]; j--) {
                dp[j] = max(dp[j], dp[j - stones[i]] + stones[i]);
            }
        }
        return sum - dp[target] - dp[target];
    }
};

494. 目标和

Leetcode链接

class Solution {
public:
    int findTargetSumWays(vector<int>& nums, int target) {
        int sum = 0;
        for (int i = 0; i < nums.size(); i++) {
            sum += nums[i];
        }
        if ((sum + target) % 2 == 1)
            return 0;
        if (abs(target) > sum)
            return 0;
        int bagsize = (sum + target) / 2;
        vector<int> dp(bagsize + 1, 0);
        dp[0] = 1;
        for (int i = 0; i < nums.size(); i++) {
            for (int j = bagsize; j >= nums[i]; j--) {
                dp[j] += dp[j - nums[i]];
            }
        }
        return dp[bagsize];
    }
};

474.一和零

Leetcode链接

class Solution {
public:
    int findMaxForm(vector<string>& strs, int m, int n) {
        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
        for (string str : strs) {
            int oneNum = 0;
            int zeroNum = 0;
            for (char c : str) {
                if (c == '0')
                    zeroNum++;
                else
                    oneNum++;
            }
            for (int i = m; i >= zeroNum; i--) {
                for (int j = n; j >= oneNum; j--) {
                    dp[i][j] = max(dp[i][j], dp[i - zeroNum][j - oneNum] + 1);
                }
            }
        }
        return dp[m][n];
    }
};

总结