代码随想录算法训练营第38天

LeetCode 322. 零钱兑换

链接

class Solution {
public:
    int coinChange(vector<int>& coins, int amount) {
        if(amount == 0) {
            return 0;
        }
        vector<int> dp(amount + 1, 0);
        for(auto i : coins) {
            if(i <= amount) {
                dp[i] = 1;
            }
        }
        for(int i = 0; i < coins.size(); i++) {
            for(int j = 0; j <= amount; j++) {
                if(j >= coins[i] && dp[j-coins[i]] != 0) {
                    if(dp[j] == 0) {
                        dp[j] = dp[j - coins[i]] + 1;
                    } else {
                        dp[j] = min(dp[j], dp[j - coins[i]] + 1);
                    }
                }
            }
        }
        if(dp[amount] == 0) {
            return -1;
        }
        return dp[amount];
    }
};

LeetCode 279. 完全平方数

链接

class Solution {
public:
    int numSquares(int n) {
        vector<int> dp(n + 1, INT_MAX);
        dp[0] = 0;
        for(int i = 1; i <= sqrt(n); i++) {
            for(int j = i * i; j <= n; j++) {
                dp[j] = min(dp[j], dp[j - i * i] + 1);
                
            }
        }
        return dp[n];
    }
};

LeetCode 139. 单词拆分

链接

class Solution {
public:
    bool wordBreak(string s, vector<string>& wordDict) {
        unordered_set<string> wordSet(wordDict.begin(), wordDict.end());
        vector<bool> dp(s.size() + 1, false);
        dp[0] = true;
        for(int i = 1; i <= s.size(); i++) {
            for(int j = 0; j < i; j++) {
                string word = s.substr(j, i - j);
                if(wordSet.find(word) != wordSet.end() && dp[j]) {
                    dp[i] = true;
                }
            }
        }
        return dp[s.size()];
    }
};