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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