Interleaving String

题目

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.

For example,
Given:
s1 = "aabcc",
s2 = "dbbca",

When s3 = "aadbbcbcac", return true.
When s3 = "aadbbbaccc", return false.

方法

二维DP问题，二维矩阵f的大小为：s1.length() * s2.length();  f[i][j] 的状态只和f[i - 1][j] 和 f[i][j - 1]相关。

    public boolean isInterleave(String s1, String s2, String s3) {    int len1 = s1.length();    int len2 = s2.length();    int len3 = s3.length();    if (len1 + len2 != len3) {    return false;    }    boolean[][] f = new boolean[len1 + 1][len2 + 1];    f[0][0] = true;    for (int i = 1; i <= len1; i++) {    f[i][0] = f[i - 1][0] && s3.charAt(i - 1) == s1.charAt(i - 1);    }    for (int j = 1; j <= len2; j++) {    f[0][j] = f[0][j - 1] && s2.charAt(j - 1) == s3.charAt(j - 1);    }        for (int i = 1; i <= len1; i++) {    for (int j = 1; j <= len2; j++) {    int len = i + j;    char c1 = s1.charAt(i - 1);    char c2 = s2.charAt(j - 1);    char c3 = s3.charAt(len - 1);    f[i][j] = (c1 == c3 && f[i - 1][j]) || (c2 == c3 && f[i][j - 1]);    }    }    return f[len1][len2];    }