43. Multiply Strings (java)

Author: bluesword12350

solution/0043.Multiply Strings/Solution.java

@@ -0,0 +1,28 @@
+class Solution {
+    public String multiply(String num1, String num2) {
+        char[] chars1 = num1.toCharArray(),chars2 = num2.toCharArray();
+        int[] result = new int[chars1.length+chars2.length];
+        int pow = result.length-1;
+        for (int i = chars1.length - 1; i >= 0; i--) {
+            int a = chars1[i] - '0';
+            int j = 0,bit = pow;
+            for (int i1 = chars2.length - 1; i1 >= 0; i1--) {
+                int b = chars2[i1] -'0';
+                j = a*b + j + result[bit];
+                result[bit--] = j%10;
+                j = j/10;
+            }
+            while (j!=0){
+                j += result[bit];
+                result[bit--] = j%10;
+                j = j/10;
+            }
+            pow--;
+        }
+        StringBuilder builder = new StringBuilder();
+        int i = 0;
+        for (; i < result.length; i++) if (result[i] != 0) break;
+        for (; i < result.length; i++) builder.append(result[i]);
+        return builder.length()==0? "0" : builder.toString();
+    }
+}