day32

322 零钱兑换

class Solution {
public:
int coinChange(vector& coins, int amount) {
vector dp(amount+1, INT_MAX);
dp[0] = 0;
for(int i = 0; i < coins.size(); ++i)
{
for(int j = coins[i]; j <= amount; ++j)
{

                    if(dp[j-coins[i]] != INT_MAX)
                    {
                        dp[j] = min(dp[j], dp[j-coins[i]] + 1);
                    }
                
            
        }
    }
    if(dp[amount] == INT_MAX) return -1;
    return dp[amount];
}

};

279 完全平方数

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

    return dp[n];
}

};

139 单词拆分

class Solution {
public:
bool wordBreak(string s, vector& wordDict) {
set wordSet;
for(string &str : wordDict)
{
wordSet.insert(str);
}
vector dp(s.size() + 1, 0);
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()];
}
};