模板：qsort+bsearch应用

 1 struct STEP
 2 {
 3     int x;
 4     int y;
 5 };
 6 
 7 int cmp(const void *a,const void *b)
 8 {
 9     STEP step1 = *((STEP *)a);
10     STEP step2 = *((STEP *)b);
11     if(step1.x == step2.x) return step1.y - step2.y;
12     else return step1.x - step2.x;
13 }
14 
15 qsort(steps,n,sizeof(STEP),cmp);
16 bsearch(&step,steps,n,sizeof(STEP),cmp);