代码随想录算法训练营Day48|贪心算法7

代码随想录算法训练营Day48|贪心算法7

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文章目录

• 代码随想录算法训练营Day48|贪心算法7
• [一、70. 爬楼梯](#一、70. 爬楼梯)
• [二、322. 零钱兑换](#二、322. 零钱兑换)
• [三、279. 完全平方数](#三、279. 完全平方数)

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一、70. 爬楼梯

class Solution {
    public int climbStairs(int n) {
        int[] dp = new int[n + 1];
        int m = 2; 
        dp[0] = 1;

        for (int i = 1; i <= n; i++) { 
            for (int j = 1; j <= m; j++) { 
                if (i >= j) 
			dp[i] += dp[i - j];
            }
        }

        return dp[n];
    }
}

二、322. 零钱兑换

class Solution {
    public int coinChange(int[] coins, int amount) {
        int max = Integer.MAX_VALUE;
        int[] dp = new int[amount + 1];
        for (int j = 0; j < dp.length; j++) {
            dp[j] = max;
        }
        dp[0] = 0;
        for (int i = 0; i < coins.length; i++) {
            for (int j = coins[i]; j <= amount; j++) {
                if (dp[j - coins[i]] != max) {
                    dp[j] = Math.min(dp[j], dp[j - coins[i]] + 1);
                }
            }
        }
        return dp[amount] == max ? -1 : dp[amount];
    }
}

三、279. 完全平方数

class Solution {
    public int numSquares(int n) {
        int max = Integer.MAX_VALUE;
        int[] dp = new int[n + 1];
        for (int j = 0; j <= n; j++) {
            dp[j] = max;
        }
        dp[0] = 0;
        for (int j = 1; j <= n; j++) {
            for (int i = 1; i * i <= j; i++) {
                dp[j] = Math.min(dp[j], dp[j - i * i] + 1);
            }
        }
        return dp[n];
    }
}