力扣---2020.5.3

53. 最大子序和

//貪心算法
class Solution {
    public int maxSubArray(int[] nums) {
        int res = nums[0];
        int sum = 0;
        for(int num:nums){
            if(sum>0){
                sum += num;
            }else{
                sum = num;
            }
            res = Math.max(res,sum);
        }
        return res;
    }
}

//動態規劃
class Solution {
    public int maxSubArray(int[] nums) {
        int[] dp = new int[nums.length];
		dp[0] = nums[0];
		int max = nums[0];
		for (int i = 1; i < nums.length; i++) {
			dp[i] = Math.max(dp[i- 1] + nums[i], nums[i]);	
			max = Math.max(dp[i],max);
		}
		return max;
    }
}

面試題49. 醜數

class Solution {
    public int nthUglyNumber(int n) {
        int a = 0, b = 0, c = 0;
        int[] dp = new int[n];
        dp[0] = 1;
        for(int i = 1; i < n; i++) {
            int n2 = dp[a] * 2, n3 = dp[b] * 3, n5 = dp[c] * 5;
            dp[i] = Math.min(Math.min(n2, n3), n5);
            if(dp[i] == n2) a++;
            if(dp[i] == n3) b++;
            if(dp[i] == n5) c++;
        }
        return dp[n - 1];
    }
}

你知道的越多，你不知道的越多。