Add solution 97.

Author: javadev

src/Algorithms/0097.interleaving-string/interleaving-string.php

@@ -0,0 +1,31 @@
+class Solution {
+
+    /**
+     * @param String $s1
+     * @param String $s2
+     * @param String $s3
+     * @return Boolean
+     */
+    function isInterleave($s1, $s2, $s3) {
+        $l1 = strlen($s1); $l2 = strlen($s2); $l3 = strlen($s3);
+        if ($l1 + $l2 != $l3) return false;
+        $dp = array_fill(0, $l1 + 1, array_fill(0, $l2 + 1, false));
+        $dp[0][0] = true;
+        for ($i = 1; $i <= $l1; $i++) {
+            if ($s1[$i - 1] == $s3[$i - 1]) $dp[$i][0] = true;
+            else break;
+        }
+
+        for ($j = 1; $j <= $l2; $j++) {
+            if ($s2[$j - 1] == $s3[$j - 1]) $dp[0][$j] = true;
+            else break;
+        }
+        for ($i = 1; $i <= $l1; $i++) {
+            for ($j = 1; $j <= $l2; $j++) {
+                    $dp[$i][$j] = ($dp[$i - 1][$j] && $s1[$i - 1] == $s3[$i + $j - 1]) 
+					|| ($dp[$i][$j - 1] && $s2[$j - 1] == $s3[$i + $j - 1]);
+            }
+        }
+        return $dp[$l1][$l2];   
+    }
+}