数组初始化memset，字符串转int数组

Author: xiangqianli

43-MultiplyStrings.cpp

@@ -0,0 +1,75 @@
+//
+//  43multiplyStrings.cpp
+//  leecode
+//
+//  Created by lixiangqian on 16/10/24.
+//  Copyright © 2016年 lixiangqian. All rights reserved.
+//
+
+#include <iostream>
+#include <stdio.h>
+#include <string>
+#include <vector>
+#include <algorithm>
+#include <map>
+#include <set>
+#include <math.h>
+#include <stdlib.h>
+using namespace std;
+int * stringToNumberList(string a, long al);
+string multiplyStrings(string num1, string num2){
+    string r;
+    if(num1=="0"||num2=="0")
+        return "0";
+    long al = num1.size();
+    long bl = num2.size();
+    int * rr = new int[al+bl+1];
+    memset(rr, 0, (al+bl+1)*4);
+    
+    int * aa = stringToNumberList(num1, al);
+    int * bb = stringToNumberList(num2, bl);
+    for(int i=0;i<bl;i++){
+        int *temp= new int[al+1];
+        memset(temp, 0, (al+1)*4);
+        int add = 0;
+        for (int j=0; j < al; j++){
+            *(temp+j) = (*(aa+j) * *(bb+i) + add)%10;
+            add = ((*(aa+j)) * (*(bb+i)) +add)/10;
+        }
+        *(temp+al)=add;
+        for(int xx=0;xx<al+1;xx++){
+            cout<<*(temp+xx)<<endl;
+        }
+        add=0;
+        for(int j=0; j<=al;j++){
+            int temprr = *(rr+i+j);
+            *(rr+i+j) = (temprr+ *(temp+j)+add)%10;
+            add =  (temprr+ (*(temp+j))+add)/10;
+        }
+        if(add>0){
+            *(rr+i+al+1) = add;
+        }
+    }
+    
+    for(long k=al+bl-2; k>=0 ;k--){
+        r +=to_string(*(rr+k));
+    }
+    if(*(rr+al+bl-1)>0 && *(rr+al+bl-1)<10){
+        r =to_string(*(rr+al+bl-1))+r;
+    }
+    return r;
+}
+int * stringToNumberList(string a, long al){
+    int *aa = new int[al];
+    for(int i=0;i<al;i++){
+        *(aa+i)=a[al-i-1]-'0';
+    }
+    return aa;
+}
+int main(){
+    string a = "12345";
+    string b = "31";
+    string result = multiplyStrings(a,b);
+    cout<<"helloworld"<<endl;
+    cout<<result<<endl;
+}