> For the complete documentation index, see [llms.txt](https://ucan.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ucan.gitbook.io/notes/sliding-window-and-and-substring-problem.md).

# Sliding Window && Substring Problem

76\. Minimum Window Substring as example

<https://leetcode.com/problems/minimum-window-substring/discuss/26808/Here-is-a-10-line-template-that-can-solve-most-'substring'-problems>

```java
class Solution {
    public String minWindow(String s, String t) {
        int[] memo = new int[128];
        for(int i = 0; i < t.length(); i++){
            memo[t.charAt(i)]++;
        }
        
        int count = t.length(), left = 0, right = 0;
        int p1=0, p2=Integer.MAX_VALUE;
        while(right<s.length()){
            // first check if the char at right is in t
            // then check if count == 0 
            // (means the window contians all characters in t)
            if(memo[s.charAt(right++)]-->0) count--;
            /* counter condition */
            while(count == 0){
                /* update result here if finding minimum*/
                if (right-left<p2-p1) {
                    //left is inclusive
                    p1=left;
                    // right is exclusive because of right++
                    p2=right;
                }
                if (memo[s.charAt(left++)]++==0) count++;
            }
            /* update d here if finding maximum*/      
        } 
        return p2==Integer.MAX_VALUE ? "" : s.substring(p1, p2);
    }
}
```


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