计算数组中最大递增数列

Question

I have to find the max increasing number sequence in this array. Does anyone know why my code doesn't run?

public class Array {

public static void main(String[] args) {

    int[] a = {4,7,15,3,9,22,36,24,28,14,19,27,30,31,2,9,29,30,16,19};

    int counter = 0;
    int maxCounter = 0;

    for (int i : a) {

        if (a[i] < a[i + 1]) {
            counter++;
        }

        if (a[i] > a[i + 1]) {
            maxCounter = counter;
            counter = 0;
        }

    }

    System.out.println(maxCounter);
}

}

Answer 1

You have two bugs, your loop should be an ordinary loop over array indices (not a for-each loop over array contents); and your setting of maxCounter should involve a comparison (not a blind assignment). Like,

for (int i = 0; i + 1 < a.length; i++) { // <-- not a for-each loop
    if (a[i] < a[i + 1]) {
        counter++;
    } else if (a[i] > a[i + 1]) { // <-- An else doesn't hurt
        // maxCounter = counter; // <-- not a blind assignment
        maxCounter = Math.max(maxCounter, counter);
        counter = 0;
    }
}

Answer 2

Working code to find the max number sequence in array.

public class Array {

public static void main(String[] args) {

int[] a = {4,7,15,3,9,22,36,24,28,14,19,27,30,31,2,9,29,30,16,19};

int counter = 1;
int maxCounter = 0;

for (int i = 0; i < a.length - 1 ; i++) {
    if (a[i] < a[i + 1]) {
        counter++;
    } else if (a[i] > a[i + 1]) {
        counter = 1;
    }

    if (counter > maxCounter) {
        maxCounter = counter;
    }
}

System.out.println(maxCounter);
}
}