C ++ classical algorithm problem - eight silver

9.Algorithm Gossip: eight silver

Explanation

Existing eight silver abcdefgh, one of which is known to counterfeit money, its weight is different from the real currency, lighter or heavier but I do not know how to use the balance with the least number of comparisons, decide which pieces of the counterfeit money, and that counterfeit lighter or heavier than the real coins.

solution

Alone seek counterfeit problem is not difficult, but the problem is to use the least restrictive of the number of comparisons, so we can not simply compare the loop is solved, we can use a decision tree (decision tree), using a tree diagram to assist in analysis and solving . A simple situation is so, we compare a + b + c and d + e + f, if they are equal, it must be a counterfeit or H g, we compare the first heavier g or H which, if severe g, and then a comparator (a true coin), if a is equal to g, the g as genuine, then h is counterfeit, since the ratio g h light and g is a genuine bill, the weight h is lighter than the true coin counterfeit.

#include<stdio.h> 
#include<stdlib.h> 
#include<time.h>

    void compare(int[], int, int, int);

    void eightcoins(int[]);

    int main(void) {
        int coins[ 8] ={
            0
        } ;
        int i;

        srand(time(NULL));


        for (i = 0; i < 8; i++) coins[i] = 10;

        printf("\n输入假币重量(比10大或小)：");
        scanf("%d", & i);
        coins[rand() % 8] = i;
        eightcoins(coins);
        printf("\n\n列出所有钱币重量：");
        for (i = 0; i < 8; i++)
            printf("%d ", coins[i]);
        printf("\n");
        return 0;
    }

    void compare(int coins[], int i, int j, int k) {
        if (coins[i] > coins[k])
            printf("\n假币 %d 较重", i + 1);

        else

    }


    printf("\n假币 %d 较轻",j+1);


    void eightcoins(int coins[]) {
        if (coins[0] + coins[1] + coins[2] ==
                coins[3] + coins[4] + coins[5]) {
            if (coins[6] > coins[7])
                compare(coins, 6, 7, 0);

            else

        }


        compare(coins, 7, 6, 0);

            else if (coins[0] + coins[1] + coins[2] > coins[3] + coins[4] + coins[5]) {
            if (coins[0] + coins[3] == coins[1] + coins[4]) compare(coins, 2, 5, 0);
            else if (coins[0] + coins[3] > coins[1] + coins[4]) compare(coins, 0, 4, 1);
            if (coins[0] + coins[3] < coins[1] + coins[4])

                compare(coins, 1, 3, 0);
        } else if (coins[0] + coins[1] + coins[2] < coins[3] + coins[4] + coins[5]) {
            if (coins[0] + coins[3] == coins[1] + coins[4]) compare(coins, 5, 2, 0);
            else if (coins[0] + coins[3] > coins[1] + coins[4]) compare(coins, 3, 1, 0);
            if (coins[0] + coins[3] < coins[1] + coins[4]) compare(coins, 4, 0, 1);
        }
    }