回答編集履歴
2
1行無駄なコードがあったので削除
test
CHANGED
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@@ -25,7 +25,6 @@
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25
25
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double binsearch(int N, int& count) {
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26
26
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count = 1;
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27
27
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double L = 0, R = N;
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28
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-
double abserr, relerr;
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29
28
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while (R - L > 0.001 && (L>0 ? (R-L)/L : 1) > 0.001) {
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30
29
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double M = (L + R) / 2;
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31
30
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double fm = f(M);
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1
f(x)の誤差を求めていたが、xの誤差だったので修正(R-Lがx誤差の最大値なのでこれを使用する)
test
CHANGED
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@@ -22,33 +22,19 @@
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22
22
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return x * x * x + x;
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23
23
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}
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24
24
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25
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-
void error(double value, double expected, double& abserr, double& relerr) {
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26
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auto result = value - expected;
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27
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abserr = result >= 0 ? result : -result;
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28
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-
relerr = abserr / expected;
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29
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-
}
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30
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-
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31
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bool is_acceptable_error(double abserr, double relerr) {
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32
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-
return abserr <= 0.001 || relerr <= 0.001;
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33
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-
}
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34
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-
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35
25
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double binsearch(int N, int& count) {
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36
26
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count = 1;
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37
27
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double L = 0, R = N;
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38
28
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double abserr, relerr;
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39
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error(f(L), N, abserr, relerr);
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40
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-
i
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29
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+
while (R - L > 0.001 && (L>0 ? (R-L)/L : 1) > 0.001) {
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41
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error(f(R), N, abserr, relerr);
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42
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if (is_acceptable_error(abserr, relerr)) return R;
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43
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-
while (true) {
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44
30
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double M = (L + R) / 2;
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45
31
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double fm = f(M);
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46
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error(fm, N, abserr, relerr);
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47
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if (is_acceptable_error(abserr, relerr)) return M;
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48
32
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if (fm >= N) R = M;
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49
33
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else L = M;
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50
34
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++count;
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51
35
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}
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36
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+
if (N - f(L) < f(R) - N) return L;
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37
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else return R;
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52
38
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}
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53
39
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54
40
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int main() {
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