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727. Minimum Window Subsequence πŸ”’

Description

Given strings s1 and s2, return the minimum contiguous substring part of s1, so that s2 is a subsequence of the part.

If there is no such window in s1 that covers all characters in s2, return the empty string "". If there are multiple such minimum-length windows, return the one with the left-most starting index.

 

Example 1:

Input: s1 = "abcdebdde", s2 = "bde"
Output: "bcde"
Explanation: 
"bcde" is the answer because it occurs before "bdde" which has the same length.
"deb" is not a smaller window because the elements of s2 in the window must occur in order.

Example 2:

Input: s1 = "jmeqksfrsdcmsiwvaovztaqenprpvnbstl", s2 = "u"
Output: ""

 

Constraints:

  • 1 <= s1.length <= 2 * 104
  • 1 <= s2.length <= 100
  • s1 and s2 consist of lowercase English letters.

Solutions

Solution 1

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class Solution:
    def minWindow(self, s1: str, s2: str) -> str:
        m, n = len(s1), len(s2)
        f = [[0] * (n + 1) for _ in range(m + 1)]
        for i, a in enumerate(s1, 1):
            for j, b in enumerate(s2, 1):
                if a == b:
                    f[i][j] = i if j == 1 else f[i - 1][j - 1]
                else:
                    f[i][j] = f[i - 1][j]
        p, k = 0, m + 1
        for i, a in enumerate(s1, 1):
            if a == s2[n - 1] and f[i][n]:
                j = f[i][n] - 1
                if i - j < k:
                    k = i - j
                    p = j
        return "" if k > m else s1[p : p + k]

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class Solution {
    public String minWindow(String s1, String s2) {
        int m = s1.length(), n = s2.length();
        int[][] f = new int[m + 1][n + 1];
        for (int i = 1; i <= m; ++i) {
            for (int j = 1; j <= n; ++j) {
                if (s1.charAt(i - 1) == s2.charAt(j - 1)) {
                    f[i][j] = j == 1 ? i : f[i - 1][j - 1];
                } else {
                    f[i][j] = f[i - 1][j];
                }
            }
        }
        int p = 0, k = m + 1;
        for (int i = 1; i <= m; ++i) {
            if (s1.charAt(i - 1) == s2.charAt(n - 1) && f[i][n] > 0) {
                int j = f[i][n] - 1;
                if (i - j < k) {
                    k = i - j;
                    p = j;
                }
            }
        }
        return k > m ? "" : s1.substring(p, p + k);
    }
}

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class Solution {
public:
    string minWindow(string s1, string s2) {
        int m = s1.size(), n = s2.size();
        int f[m + 1][n + 1];
        memset(f, 0, sizeof(f));
        for (int i = 1; i <= m; ++i) {
            for (int j = 1; j <= n; ++j) {
                if (s1[i - 1] == s2[j - 1]) {
                    f[i][j] = j == 1 ? i : f[i - 1][j - 1];
                } else {
                    f[i][j] = f[i - 1][j];
                }
            }
        }
        int p = 0, k = m + 1;
        for (int i = 1; i <= m; ++i) {
            if (s1[i - 1] == s2[n - 1] && f[i][n]) {
                int j = f[i][n] - 1;
                if (i - j < k) {
                    k = i - j;
                    p = j;
                }
            }
        }
        return k > m ? "" : s1.substr(p, k);
    }
};

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func minWindow(s1 string, s2 string) string {
    m, n := len(s1), len(s2)
    f := make([][]int, m+1)
    for i := range f {
        f[i] = make([]int, n+1)
    }
    for i := 1; i <= m; i++ {
        for j := 1; j <= n; j++ {
            if s1[i-1] == s2[j-1] {
                if j == 1 {
                    f[i][j] = i
                } else {
                    f[i][j] = f[i-1][j-1]
                }
            } else {
                f[i][j] = f[i-1][j]
            }
        }
    }
    p, k := 0, m+1
    for i := 1; i <= m; i++ {
        if s1[i-1] == s2[n-1] && f[i][n] > 0 {
            j := f[i][n] - 1
            if i-j < k {
                k = i - j
                p = j
            }
        }
    }
    if k > m {
        return ""
    }
    return s1[p : p+k]
}

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function minWindow(s1: string, s2: string): string {
    const m = s1.length;
    const n = s2.length;
    const f: number[][] = Array(m + 1)
        .fill(0)
        .map(() => Array(n + 1).fill(0));
    for (let i = 1; i <= m; ++i) {
        for (let j = 1; j <= n; ++j) {
            if (s1[i - 1] === s2[j - 1]) {
                f[i][j] = j === 1 ? i : f[i - 1][j - 1];
            } else {
                f[i][j] = f[i - 1][j];
            }
        }
    }
    let p = 0;
    let k = m + 1;
    for (let i = 1; i <= m; ++i) {
        if (s1[i - 1] === s2[n - 1] && f[i][n]) {
            const j = f[i][n] - 1;
            if (i - j < k) {
                k = i - j;
                p = j;
            }
        }
    }
    return k > m ? '' : s1.slice(p, p + k);
}

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