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  • 376. Wiggle Subsequence

    A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The first difference (if one exists) may be either positive or negative. A sequence with fewer than two elements is trivially a wiggle sequence.

    For example, [1,7,4,9,2,5] is a wiggle sequence because the differences (6,-3,5,-7,3) are alternately positive and negative. In contrast, [1,4,7,2,5] and [1,7,4,5,5] are not wiggle sequences, the first because its first two differences are positive and the second because its last difference is zero.

    Given a sequence of integers, return the length of the longest subsequence that is a wiggle sequence. A subsequence is obtained by deleting some number of elements (eventually, also zero) from the original sequence, leaving the remaining elements in their original order.

    Examples:

    Input: [1,7,4,9,2,5]
    Output: 6
    The entire sequence is a wiggle sequence.
    
    Input: [1,17,5,10,13,15,10,5,16,8]
    Output: 7
    There are several subsequences that achieve this length. One is [1,17,10,13,10,16,8].
    
    Input: [1,2,3,4,5,6,7,8,9]
    Output: 2

    AC代码,runtime 0ms.

     1 class Solution {
     2 public:
     3     int wiggleMaxLength(vector<int>& nums) {
     4         if(nums.empty())return 0;
     5         int ret=1,length=nums.size(),diff,bg=1;
     6         for(;bg<length;bg++){
     7             diff=nums[bg]-nums[bg-1];
     8             if(diff!=0){
     9                 ret++;
    10                 break;
    11             }
    12             if(bg==length)return ret;
    13         }
    14         for(int i=bg+1;i<length;i++){
    15             int tmpdiff=nums[i]-nums[i-1];
    16             if(tmpdiff==0)continue;
    17             if(tmpdiff*diff<0){
    18                 diff=tmpdiff;
    19                 ret++;
    20             }
    21         }
    22         return ret;
    23     }
    24 };
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  • 原文地址:https://www.cnblogs.com/Z-Sky/p/5700774.html
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