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// 592. Fraction Addition and Subtraction
#include "leetcode.h"
/*
* given a string 'expression' representing an expression of fraction addition
* and subtraction, return the calculation result in string format. the final
* result should an irreducible fraction. if your final result is an integer,
* change it to the format of a fraction has a denominator 1. so in this case, 2
* should be converted to "2/1"
*/
int gcd(int a, int b) {
if (!(a % b))
return b;
return gcd(b, a % b);
}
int numerator(int i, char *exp) {
char *tmp = "";
while (exp[i] != '/') {
tmp += exp[i];
i++;
}
return atoi(tmp);
}
int denominator(int i, char *exp) {
char *tmp = "";
while (exp[i] != '/') {
tmp += exp[i];
i++;
}
return atoi(tmp);
}
char *fractionAddition(char *expression) {
int s1 = 1, i = 0;
if (expression[0] == '-') {
s1 = -1;
i++;
}
int n1 = numerator(i, expression);
i++;
int d1 = denominator(i, expression);
while (i < strlen(expression)) {
int s2 = expression[i] == '-' ? -1 : 1;
i++;
int n2 = numerator(i, expression);
i++;
int d2 = denominator(i, expression);
int lcm = (d2 * d1) / gcd(d1, d2);
n1 = (s1 * n1 * (lcm / d1) + s2 * n2 * (lcm / d2));
d1 = lcm;
if (n1 < 0) {
s1 = -1;
n1 *= -1;
} else
s1 = 1;
}
int g = gcd(n1, d1);
if (g > 1) {
n1 /= g;
d1 /= g;
}
int len = 0;
len += (s1 == -1) ? 1 : 0;
len += snprintf(NULL, 0, "%d", n1);
len += 1;
len += snprintf(NULL, 0, "%d", d1);
char *res = (char *)malloc(len + 1);
res[0] = '\0';
if (s1 == -1)
strcat(res, "-");
char buffer[50];
sprintf(buffer, "%d", n1);
strcat(res, buffer);
strcat(res, "/");
sprintf(buffer, "%d", d1);
strcat(res, buffer);
return res;
}
int main() {
char *e1 = "-1/2+1/2", *e2 = "-1/2+1/2+1/3", *e3 = "1/3-1/2";
printf("%s\n", fractionAddition(e1)); // expect: 0/1
printf("%s\n", fractionAddition(e2)); // expect: 1/3
printf("%s\n", fractionAddition(e3)); // expect: -1/6
}
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