长安城商人王掌柜收到来自 6 个西域国家的货物，重量记录在数组 weights 中，每件货物重量大于 0，且 6 个货物的重量不相同。王掌柜想知道最重和次重的货物重量，以便决定将最重的作为“样品”展示，次重的作为“备用样品”。以下程序段可以正确求出最重重量（max1）和次重重量（max2）的有？

int max1 = weights[0], max2 = weights[0];
for(int i=1; i<6; i++) {
    if(weights[i] > max1) {
        max2 = max1;
        max1 = weights[i];
    }
    else if(weights[i] > max2) {
        max2 = weights[i];
    }
} 

int max1 = weights[0], max2 = weights[1];
if(max1 < max2) swap(max1, max2);
for(int i=2; i<6; i++) {
    if(weights[i] > max1) {
        max2 = max1;
        max1 = weights[i];
    }
    else if(weights[i] > max2) {
        max2 = weights[i];
    }
}

int max1 = weights[0], max2 = weights[0];
for (int i=1; i<6; i++) {
    if(weights[i] > max1) max1 = weights[i];
    if(weights[i] > max2 && weights[i] != max1) max2 = weights[i];
}

int max1=0, max2=0;
for (int i=0; i<6; i++) {
    if(weights[i] > max1) {
        max1 = weights[i];
    }
}
for (int i=0; i<6; i++) {
    if(weights[i] > max2 && weights[i] != max1) {
        max2 = weights[i];
    }
}