[08/13/13] Challenge #135 [Easy] Arithmetic Equations (2nd Attempt)

gistfile1.cpp

#include <stdlib.h>
#include <stdio.h>
#include <vector>
using namespace std;

struct ExpressionElement {
  bool isValue;
	union {
		int value;
		char op;
	} data;
};

int main()
{
	int min, max;
	char opChars[3] = { '+', '-', 'x' };
	scanf("%d %d", &min, &max);

	int consts[4];
	char ops[3];

	// Infinite loop unless user exists...
	bool correct = true;
	int correctResult = 0;
	while(true)
	{
		// If correct, generate new challenge
		if(correct)
		{
			for(int i = 0; i < 4; i++)
				consts[i] = min + rand() % (max - min + 1); // +1 since we're inclusive
			for(int i = 0; i < 3; i++)
				ops[i] = opChars[rand() % 3];
			
			// Place equation into ExpressionElement list, so we can compute a solution
			vector< ExpressionElement > expressionList;
			for(int i = 0; i < 4; i++)
			{
				ExpressionElement element;
				element.isValue = true;
				element.data.value = consts[i];
				expressionList.push_back(element);
				
				if(i < 3)
				{
					element.isValue = false;
					element.data.op = ops[i];
					expressionList.push_back(element);
				}
			}

			// Do all multiplication first, storing the result to the right of the op
			for(int i = 0; i < expressionList.size() / 2; i++)
			{
				int index = i * 2;
				ExpressionElement arg0 = expressionList.at(index + 0);
				ExpressionElement op =	 expressionList.at(index + 1);
				ExpressionElement arg1 = expressionList.at(index + 2);

				if(arg0.isValue && !op.isValue && arg1.isValue && op.data.op == 'x')
				{
					expressionList.erase(expressionList.begin() + index);
					expressionList.erase(expressionList.begin() + index);
					
					expressionList.at(index).data.value = arg0.data.value * arg1.data.value;
					i--;
				}
			}

			// Add/sub
			for(int i = 0; i < expressionList.size() / 2; i++)
			{
				int index = i * 2;
				ExpressionElement arg0 = expressionList.at(index + 0);
				ExpressionElement op =	 expressionList.at(index + 1);
				ExpressionElement arg1 = expressionList.at(index + 2);

				if(arg0.isValue && !op.isValue && arg1.isValue)
				{
					expressionList.erase(expressionList.begin() + index);
					expressionList.erase(expressionList.begin() + index);
					
					if(op.data.op == '+')
						expressionList.at(index).data.value = arg0.data.value + arg1.data.value;
					else
						expressionList.at(index).data.value = arg0.data.value - arg1.data.value;
					i--;
				}
			}
			
			correctResult = expressionList.at(0).data.value;
			correct = false;
		}

		printf("%d %c %d %c %d %c %d\n", consts[0], ops[0], consts[1], ops[1], consts[2], ops[2], consts[3]);

		char input[512];
		fgets(input, 511, stdin);

		if(input[0] == 'q' || input[0] == 'Q')
		{
			break;
		}
		else
		{
			int value = -1;
			int scanned = sscanf(input, "%d", &value);
			if(scanned != 1)
				printf("Incorrect input format, try again\n");
			else if(value != correctResult)
				printf("Incorrect...\n");
			else if(value == correctResult)
			{
				printf("Correct!\n");
				correct = true;
			}
		}
	}

	// All done
	return 0;
}