c - qsort() 图结构数组

Question

struct Edge
{
    int src, dest, weight;
}; typedef struct Edge Edge;

struct Graph
{
    int V, E;
    Edge* edge;
}; typedef struct Graph Graph;

我有一个这样的图形结构。我正在尝试使用 qsort 按权重的递增顺序对所有边进行排序。主要是:

Graph* graph = (Graph*)malloc(sizeof(Graph));
qsort(graph->edge, graph->E, sizeof(graph->edge[0]), myComp);

Mycomp 函数:

    int myComp(const void* a, const void* b)
{
    Edge* a1 = (Edge*)a;
    Edge* b1 = (Edge*)b;
    return a1->weight > b1->weight;
}

毕竟，我尝试打印qsort前后的每条边，顺序已经改变但不是正确的顺序。任何人都可以帮助解决这些问题吗？我的代码哪一部分有问题？

Answer 1

return a1->weight > b1->weight;

应该是

return a1->weight - b1->weight;

来自手册:

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.