题解 | #求解立方根#
求解立方根
http://www.nowcoder.com/practice/caf35ae421194a1090c22fe223357dca
二分
#include <stdio.h>
float getValWhenMore0(float left, float right, float val)
{
float mid = (left + right) / 2.0;
while(1){
if(mid * mid * mid > val){
if(mid * mid * mid - val <= 0.01){
return mid;
}
else{
right = mid;
mid = (left + right) / 2.0;
}
}
else if(mid * mid * mid < val){
if(val - mid * mid * mid <= 0.01){
return mid;
}
else{
left = mid;
mid = (left + right) / 2.0;
}
}
else{
return mid;
}
}
}
float getValWhenLess0(float left, float right, float val)
{
float mid = (left + right) / 2.0;
while(1){
if(mid * mid * mid < val){
if(val - mid * mid * mid <= 0.01){
return mid;
}
else{
right = mid;
mid = (left + right) / 2.0;
}
}
else if(mid * mid * mid > val){
if(mid * mid * mid - val <= 0.01){
return mid;
}
else{
left = mid;
mid = (left + right) / 2.0;
}
}
else{
return mid;
}
}
}
int main()
{
float val;
while(scanf("%f", &val) != EOF){
float mid, left = 0.0, right = val;
if(val >= 1.0){
mid = getValWhenMore0(left, right, val);
}
else if(val <= -1.0){
mid = getValWhenLess0(left, right, val);
}
else if(val > 0 && val < 1.0){
left = val;
right = 1.0;
mid = getValWhenMore0(left, right, val);
}
else if(val > -1.0 && val < 0.0){
left = val;
right = -1.0;
mid = getValWhenLess0(left, right, val);
}
printf("%0.1f\n", mid);
}
}
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