题解 | #浮点数加法#

#include <iostream>
#include <cstring>
#define MAX 1000
using namespace std;

int add(char a[], char b[], char c[], bool msb_carry, int carry, bool isINT) {
    //msb_carry=true return carry
    //msb_carry=false set carry as new msb
    //isINT=true calc int ;false =calc frac
    int alen = strlen(a), blen = strlen(b);
    int array_max = max(alen, blen);
    int i, j, sum = 0;

    if (isINT) { //整数部分
        c[max(alen, blen)] = '\0';
        for (i = alen - 1, j = blen - 1; i >= 0 || j >= 0; i--, j--) {
            int adigit = (i >= 0 ? a[i] - '0' : 0);
            int bdigit = (j >= 0 ? b[j] - '0' : 0);
            sum = adigit + bdigit + carry;
            carry = sum / 10;
            c[max(i, j)] = sum % 10 + '0';
        }
    } else { //小数部分
        c[array_max] = '\0';
        for (i = array_max - 1; i >= 0; i--) {
            int adigit = (i < alen ? a[i] - '0' : 0);
            int bdigit = (i < blen ? b[i] - '0' : 0);
            sum = adigit + bdigit + carry;
            carry = sum / 10;
            c[i] = sum % 10 + '0';
        }
    }
    if (msb_carry) return carry;
    else if (carry == 1) {
        for (int k = strlen(c) + 1; k >= 1; k--)
            c[k] = c[k - 1];
        c[0] = '1';
        return 0;
    } else return 0;
}

void separate(char a[], char ai[], char af[]) {
    int alen = strlen(a);
    int i, f, d;
    for (i = 0; i < alen; i++) {
        if (a[i] == '.') break;
        else ai[i] = a[i];
    }
    ai[++i] = '\0'; //ai末尾添0
    d = i;
    for (f = 0; f <= alen - d; f++, i++) {
        af[f] = a[i];
    }
    af[++f] = '\0'; //af末尾添0
}

int main() {
    char a[MAX], b[MAX];
    char ai[MAX], af[MAX];
    char bi[MAX], bf[MAX];
    char resi[MAX], resf[MAX];
    scanf("%s", a);
    scanf("%s", b);
    separate(a, ai, af);
    separate(b, bi, bf);
    add(ai, bi, resi, false, add(af, bf, resf, true, 0, false), true);
    printf("%s.%s", resi, resf);
}