45 lines
No EOL
1.1 KiB
Rust
45 lines
No EOL
1.1 KiB
Rust
pub use inst::pow;
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mod inst {
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pub type T = int;
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pub const bits: uint = uint::bits;
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/// Returns `base` raised to the power of `exponent`
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pub fn pow(base: int, exponent: uint) -> int {
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if exponent == 0u {
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//Not mathemtically true if ~[base == 0]
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return 1;
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}
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if base == 0 { return 0; }
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let mut my_pow = exponent;
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let mut acc = 1;
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let mut multiplier = base;
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while(my_pow > 0u) {
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if my_pow % 2u == 1u {
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acc *= multiplier;
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}
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my_pow /= 2u;
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multiplier *= multiplier;
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}
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return acc;
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}
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#[test]
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fn test_pow() {
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assert (pow(0, 0u) == 1);
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assert (pow(0, 1u) == 0);
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assert (pow(0, 2u) == 0);
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assert (pow(-1, 0u) == 1);
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assert (pow(1, 0u) == 1);
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assert (pow(-3, 2u) == 9);
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assert (pow(-3, 3u) == -27);
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assert (pow(4, 9u) == 262144);
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}
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#[test]
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fn test_overflows() {
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assert (max_value > 0);
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assert (min_value <= 0);
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assert (min_value + max_value + 1 == 0);
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}
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} |