Thread: Anyone taken a C test for a job before?

Arright. I did the test probably a month ago. It was the same as yours. I did quite well, imho, but nobody contacted me ever since. Time to post the working solution to the first problem, then.

Code:

//1. Write a function that given a string of digits and a target value, prints where to put +'s and *'s between the digits so they combine exactly to the target value. Note there may be more than one answer, it doesn't matter which one you print.
//Examples:
//"1231231234",11353 -> "12*3+1+23*123*4"
//"3456237490",1185 -> "3*4*56+2+3*7+490"
//"3456237490",9191 -> "no solution"
//
//Solution:

#include <stdio.h>
#include <string.h>

 
const char symb[3]= {'+','*',' '};



void print_sequence(FILE* file, char* deststr, int nchar)
{
	int i;
	for(i=0; i<nchar && deststr[i]!='\0'; i++) {
		if(deststr[i]==' ') continue;
		fprintf(file, "%c", deststr[i]);
	}
	return;
}



void transform_n_check(char* deststr, const int ndigs, const int target, short *done) {

	char strcopy[ndigs*2];
	char* add[ndigs];
	char *p;
	int i= 0;
	int total= 0;

	for(i=0; i<ndigs*2; i++)
		strcopy[i]= deststr[i];

	// find all the addends
	i= 0;
	add[i]= strtok(strcopy, "+");
	while( (p=strtok(NULL,"+")) != NULL ) {
		add[++i]= p;
	}
	int na= i+1;
	
	char *mult[ndigs];
	int totmult;

	for(i=0; i<na; i++) {
		// find all the multiplications composing this addend
		int j= 0;
		mult[j]= strtok(add[i],"*");
		while( (p=strtok(NULL,"*")) != NULL ) {
			mult[++j]= p;
		}	

		int nm= j+1;

		// multiply the multiplicands of this addend together
		totmult= 1;
		for(j=0; j<nm; j++) {
			int k;
			int temp= 0;
			for(k=0; k<strlen(mult[j]); k++) {		// atoi skipping spaces indicating "no operator"
				if(mult[j][k]==' ') continue;	
				temp*= 10;
				temp+= mult[j][k]-'0';
			}
			totmult*= temp;
		}	

		
		total+= totmult;
	}

	*done= (total==target);

	return;
}





void build(int level, char *deststr, const int ndigs, const int target, short* done) {

	if(level==ndigs-1) {
		transform_n_check(deststr, ndigs, target, done);
//		if(*done) {
//			print_sequence(stdout,deststr,ndigs*2-1);
//		}
		return;
	}
	
	int ns;

	for(ns=0; ns<3 && !*done; ns++) {					// !*done avoids printing multiple solutions
		deststr[level2pos(level)]= symb[ns];
		build(level+1,deststr,ndigs,target,done);
	}
	
//	if(level==0 && !*done)
//		strcpy(deststr,"no solution");

	return;
	
}




int level2pos(const int level) {
	return level*2+1;
}




void calculus(char* str, const int target) {
	
	const int ndigs= strlen(str);
	int totdlen= ndigs*2-1;
	char deststr[totdlen+1];
	
	int i;
	for(i=0; i<ndigs; i++) {
		deststr[i*2]= str[i];
		deststr[i*2+1]= '!';
	}
	deststr[totdlen]= '\0';

	int ncombs= 3^(ndigs-1);

	// str= "1234"
	// deststr= "1+2+3+4"

	printf("\"%s\", %d -> \"", str, target);
	short done= 0;
	build(0, deststr, ndigs, target, &done);
	if(done)
		print_sequence(stdout,deststr,totdlen*2);
	else
		printf("no solution");
	printf("\"\n");
	return;	
}




int main() {
	calculus("1234",408);
	calculus("1231231234",11353); // "12*3+1+23*123*4"
	calculus("3456237490",1185);  // "3*4*56+2+3*7+490"
	calculus("3456237490",9191);  // "no solution"
}