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  • LeetCode 525. Contiguous Array

    525. Contiguous Array

    Description Submission Solutions

    • Total Accepted: 2476
    • Total Submissions: 8220
    • Difficulty: Medium
    • Contributors: bishwa 

    Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.

    Example 1:

    Input: [0,1]
    Output: 2
    Explanation: [0, 1] is the longest contiguous subarray with equal number of 0 and 1.

    Example 2:

    Input: [0,1,0]
    Output: 2
    Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.

    Note: The length of the given binary array will not exceed 50,000.

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    【题目分析】

    这个题目的意思是给定一个只包含0,1的整数数组,找到数组中最长的一个子序列,该序列中1的个数和0的个数相同。


    【思路】

    这个题目真的很有意思啊,我感觉自己想不到这么好的解法。

    看大家的解题思路如下:

    The idea is to change 0 in the original array to -1. Thus, if we find SUM[i, j] == 0 then we know there are even number of -1 and 1 between index i and j. Also put the sum to index mapping to a HashMap to make search faster.


    【java代码】

     1 public class Solution {
     2     public int findMaxLength(int[] nums) {
     3         for(int i = 0; i < nums.length; i++) {
     4             if(nums[i] == 0) nums[i] = -1;
     5         }
     6         
     7         int res = 0, sum = 0;
     8         Map<Integer, Integer> map = new HashMap<>();
     9         map.put(0, -1);
    10         
    11         for(int i = 0; i < nums.length; i++) {
    12             sum += nums[i];
    13             if(map.containsKey(sum)) {
    14                 res = Math.max(res, i-map.get(sum));
    15             }
    16             else {
    17                 map.put(sum, i);
    18             }
    19         }
    20         
    21         return res;
    22     }
    23 }
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  • 原文地址:https://www.cnblogs.com/liujinhong/p/6472580.html
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