原题链接
郁闷,WA了3次,好在最终找到了原因,qsort的cmp函数有问题,对于浮点数,比较的时候一定要注意。
#include <stdio.h>
#include <stdlib.h>
struct Node{
int x, y;
double rate;
};
int cmp(const void *a, const void *b){
if ((*(Node *)b).rate - (*(Node *)a).rate < 0)
return -1;
}
int main(){
int m, n, i;
double s;
while(scanf("%d%d", &m, &n), m != -1 || n != -1){
Node *a = (Node *)malloc(sizeof(Node) * n);
for(i = 0; i != n; ++i){
scanf("%d%d", &a[i].x, &a[i].y);
a[i].rate = a[i].x * 1.0 / a[i].y;
}
qsort(a, n, sizeof(Node), cmp);
for(i = s = 0; m > 0 && i < n; ++i){
if(a[i].y <= m){
s += a[i].x;
m -= a[i].y;
}else{
s += m * a[i].rate;
break;
}
}
printf("%.3lf\n", s);
free(a);
}
return 0;
}