209. 长度最小的子数组
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class Solution {public int minSubArrayLen(int target, int[] nums) {int n = nums.length;int res = Integer.MAX_VALUE;int sum = 0;int l = 0;for(int i = 0; i < n ; i++){//1缩小窗口//1.1右端往右走sum += nums[i];while(sum >= target){//满足要求 到 不满足要求//满足要求求一下resres = Math.min(res, i - l + 1);//1.2左端往右走sum -= nums[l];l++;}}return res == Integer.MAX_VALUE ? 0 : res ;}
}
713. 乘积小于 K 的子数组
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class Solution {public int numSubarrayProductLessThanK(int[] nums, int k) {if (k <= 1) return 0;int n = nums.length;int res = 0;int sum = 1;int l = 0;for(int i = 0; i < n ; i++){sum *= nums[i];//右端往右走while(sum >= k){//不满足要求 到 满足要求sum /= nums[l];l++;}//满足要求了求一下resres += i - l + 1;}return res;}
}
3. 无重复字符的最长子串
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class Solution {public int lengthOfLongestSubstring(String s) {char[] a = s.toCharArray();int n = a.length;int res = 0;int l = 0;Map<Character, Integer> map = new HashMap<>();for(int r = 0; r < n; r++){map.put(a[r],map.getOrDefault(a[r],0) + 1);while(map.get(a[r]) > 1){//不满足条件map.put(a[l], map.get(a[l]) - 1);l++;}//满足条件res = Math.max(res, r - l + 1);}return res;}
}