ok

NoteXYX · NoteXYX · commit 21a62da4b114 · 2020-08-14T00:45:49.000+08:00
diff --git a/src/com/leetcode/Main43.java b/src/com/leetcode/Main43.java
@@ -0,0 +1,48 @@
+package com.leetcode;
+
+/**
+ * 43. 字符串相乘
+ * 给定两个以字符串形式表示的非负整数 num1 和 num2，返回 num1 和 num2 的乘积，它们的乘积也表示为字符串形式。
+ *
+ * 示例 1:
+ *
+ * 输入: num1 = "2", num2 = "3"
+ * 输出: "6"
+ * 示例 2:
+ *
+ * 输入: num1 = "123", num2 = "456"
+ * 输出: "56088"
+ */
+public class Main43 {
+    public String multiply(String num1, String num2) {
+        if (num1.equals("0") || num2.equals("0")) {
+            return "0";
+        }
+        StringBuilder res = new StringBuilder();
+        int m = num1.length();
+        int n = num2.length();
+        int[] tmp = new int[m+n];
+        for (int i = m-1; i >= 0; i--) {
+            int x = num1.charAt(i) - '0';
+            for (int j = n-1; j >= 0; j--) {
+                int y = num2.charAt(j) - '0';
+                int sum = tmp[i+j+1] + x * y;
+                tmp[i+j+1] = sum % 10;
+                tmp[i+j] += sum / 10;
+            }
+        }
+        for (int i = 0; i < m+n; i++) {
+            if (i == 0 && tmp[i] == 0)
+                continue;
+            res.append(tmp[i]);
+        }
+        return res.toString();
+    }
+
+    public static void main(String[] args) {
+        Main43 m = new Main43();
+        String num1 = "123";
+        String num2 = "456";
+        System.out.println(m.multiply(num1, num2));
+    }
+}
