大数加法

#include<iostream>



#include<stdio.h>



#include<string.h>



using namespace std;



char * add(char *a, char*b) {



  int la = strlen(a);



  int lb = strlen(b);



  char result[la+lb+2];



  int p_r = 0;



  memset(result, 0, sizeof(result));



  int crease = 0;



  while (la-- && lb--) {



    int tmp = int(a[la] - '0' + b[lb] - '0') + crease;



    result[p_r] = (tmp % 10) + '0';



    crease = tmp / 10;



    p_r++;



  }



  while (la>=0) {



    int tmp = crease + int(a[la] - '0');



    result[p_r] = (tmp%10) + '0';



    crease = tmp/ 10;



    p_r++;



    la--;



  }



  while (lb>=0) {



    int tmp = crease + int(b[lb] - '0');



    result[p_r] = (tmp%10) + '0';



    crease = tmp/ 10;



    p_r++;



    lb--;



  }



  if ( crease > 0 ){



    result[p_r] = crease + '0';



    p_r++;



  }



  result[p_r]='\0';



  for (int i=0; i<strlen(result)/2; ++i) {



    char tmp = result[strlen(result)-i-1];



    result[strlen(result)-i-1] = result[i];



    result[i] = tmp;



  }



  return result;



}

int main(int argc, char** argv){

  char *a = "123456";

  char *b = "9999";

  char * result = add(a,b);

  printf ("%s+%s=%s", a, b, result);

  return 0;

}

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