动态规划之最长子序列之和

剑指 Offer 42 leetcode: https://leetcode-cn.com/problems/lian-xu-zi-shu-zu-de-zui-da-he-lcof/

/**
* 借助数组
* @param nums
* @return
*/
public static int maxLength(int[] nums) {
if (nums == null || nums.length < 1) {
return 0;
}
int[] dp = new int[nums.length];
dp[0] = nums[0];
int max = dp[0];
for (int i = 1; i < dp.length; i++) {
System.out.println("i = " + i);
if (dp[i - 1] <= 0) {
dp[i] = nums[i];
} else {
dp[i] = dp[i - 1] + nums[i];
}
max = Math.max(max, dp[i]);
}

    return max;
    
}

/**
 * 其实只需要用到前一个值，滚动数组
 * @param nums
 * @return
 */
public static int maxLength01(int[] nums) {
    if (nums == null || nums.length < 1) {
        return 0;
    }
    int i = 1;
    int prev = nums[0];
    int max = prev;
    while ( i < nums.length ) {
        
        if (prev <= 0) {
            prev = nums[i];
        } else {
            prev = prev + nums[i];
        }
        max= Math.max(prev, max);
        i ++;
        
    }
    return max;
    
}