209. Minimum Size Subarray Sum
2017-01-22 15:02
288 查看
Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn’t one, return 0 instead.
For example, given the array [2,3,1,2,4,3] and s = 7,
the subarray [4,3] has the minimal length under the problem constraint.
循环遍历数组,如果小于s,循环加上nums[big++];
循环遍历数组,如果sum>=s,就先min = Math.min(min,big-small);然后sum -= nums[small++];
如果使用小于等于s,请看如下情况:[2,3,1,1,1,1,1] and s=5,那么还要加上1。之后的第三步就不对了。无论如何都得不到正确的结果。
For example, given the array [2,3,1,2,4,3] and s = 7,
the subarray [4,3] has the minimal length under the problem constraint.
思考:
使用两个指针small,big,并初始化sum = 0;循环遍历数组,如果小于s,循环加上nums[big++];
循环遍历数组,如果sum>=s,就先min = Math.min(min,big-small);然后sum -= nums[small++];
细节问题:
步骤二,为什么不使用小于等于s呢?如果使用小于等于s,请看如下情况:[2,3,1,1,1,1,1] and s=5,那么还要加上1。之后的第三步就不对了。无论如何都得不到正确的结果。
代码:
public int minSubArrayLen1(int s, int[] nums) { // Arrays.sort(nums); int small = 0; int big = 0; int len = nums.length; int sum = 0; int min = Integer.MAX_VALUE; while(small<len && big<len){ while(sum < s && big<len){ //sum<s 还是sum<=s? sum += nums[big]; big++; } while(sum >= s && small<big){//如果是 sum>=s 呢? min = Math.min(min, big-small); sum -= nums[small]; small++; } } return min==Integer.MAX_VALUE?0:min; }
总结:
这道题考察了双指针的移动。对于双指针的移动,有三种情况:1.从左边开始移动2.从右边开始移动(这两种情况容易想到)3.从中间开始向两端移动。4.从两端向中间开始移动。本题是第一种情况。相关文章推荐
- 209. Minimum Size Subarray Sum LeetCode
- 209. Minimum Size Subarray Sum
- [leetcode]209. Minimum Size Subarray Sum
- [LeetCode] 209. Minimum Size Subarray Sum
- 209. Minimum Size Subarray Sum
- 209. Minimum Size Subarray Sum(很重要)
- [leetcode] 209. Minimum Size Subarray Sum
- leetcode 209. Minimum Size Subarray Sum
- 209. Minimum Size Subarray Sum
- 209. Minimum Size Subarray Sum 【M】【35】
- leetcode题解-209. Minimum Size Subarray Sum
- 【leetcode】209. Minimum Size Subarray Sum
- leetcode ----209. Minimum Size Subarray Sum
- 209. Minimum Size Subarray Sum**
- 209. Minimum Size Subarray Sum
- Middle-题目87:209. Minimum Size Subarray Sum
- leetcode209. Minimum Size Subarray Sum
- [LeetCode] 209. Minimum Size Subarray Sum
- LeetCode 209. Minimum Size Subarray Sum
- LeetCode 209. Minimum Size Subarray Sum