[英]Why is the placement of variable declaration giving different results?
#include <stdio.h>
int order = 3;
int wt[10] = {2,1,3};
int price [10] = {100,50,150};
int maxW = 5;
void fracK() {
int curr_weight, i, max_i; // <<<<
float tot_price; // <<<<
int used[10]; // <<<<
//inititialising all used elements to 0
for (i = 0; i < order; ++i) {
used[i] = 0;
}
curr_weight = maxW;
while (curr_weight > 0) {
max_i = -1;
for (i = 0; i < order; ++i) {
if ((used[i] == 0) && ((max_i == -1) || ((float)price[i]/wt[i] > (float)price[max_i]/wt[max_i]))){
max_i = i;
}
}
used[max_i] = 1;
curr_weight -= wt[max_i];
tot_price += price[max_i];
if (curr_weight >= 0) {
continue;
}else {
tot_price -= price[max_i];
tot_price += (1 + (float)curr_weight/wt[max_i]) * price[max_i];
}
}
printf("%f", tot_price);
}
//driver function
int main(int argc, char *argv[]) {
fracK();
return 0;
}
in lines 9 to 11, if I declare float
in the second or third line ie line 10 or 11, the final value returned is 197040072659526240000000000000000.000000
, which is not my expected value.在第 9 到 11 行中,如果我在第二行或第三行(即第 10 行或第 11 行)声明float
,则返回的最终值为197040072659526240000000000000000.000000
,这不是我的预期值。 However, when I declare the float
variable in the first line, ie line 9, the final value returned is 250.000000
which is my expected value.但是,当我在第一行(即第 9 行)声明float
变量时,最终返回的值为250.000000
,这是我的预期值。
It should be:它应该是:
float tot_price = 0;
then the placement probably will not matter.那么位置可能无关紧要。 As is now, the code is adding numbers to uninitialized variable, which will not have predictable results.和现在一样,代码将数字添加到未初始化的变量中,这不会有可预测的结果。
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