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binary search sqrt
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| #include <stdio.h> | |
| #include <stdlib.h> | |
| #define PRECISION 0.0000001 | |
| #define POW2(x) x * x | |
| #define ABS(x) x > 0 ? x : -x | |
| #define TEST(VALUE, EXPECT) {\ | |
| printf("testing: %0.4f expecting %0.4f", VALUE, EXPECT);\ | |
| if (ABS(_sqrt(VALUE) - EXPECT) <= PRECISION)\ | |
| printf("\n PASSED!\n");\ | |
| else printf("\n FAIL %0.4f is not equal of %0.4f\n", _sqrt(VALUE), EXPECT);\ | |
| } | |
| double _sqrt(double number) | |
| { | |
| double start = 0, end = number, middle = 0; | |
| double guess_result = start; | |
| while ((end - start) > PRECISION) | |
| { | |
| middle = (start + end) / 2.0; | |
| guess_result = POW2(middle); | |
| if (guess_result == number) | |
| { | |
| return middle; // exact result | |
| } | |
| else if (guess_result < number) | |
| { | |
| start = middle; | |
| } | |
| else // guess_result > number | |
| { | |
| end = middle; | |
| } | |
| } | |
| // in case of not exact match, return the most near number as possible | |
| // due to PRECISION | |
| return middle; | |
| } | |
| int main(){ | |
| TEST(0.0, 0.0) | |
| TEST(1.0, 1.0) | |
| TEST(9.0, 3.0) | |
| TEST(16.0, 4.0) | |
| TEST(1.520, 1.2328828005937953) | |
| TEST(3.0, 1.7320508075688772); | |
| } |
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