找到可能生成的字符串 T 的可能最小不平衡度的 C++ 程序
假设我们有具有可能字符 '0'、'1'或 '?' 的字符串 S。我们想通过用 0 或 1 替换每次出现的 '?' 来生成字符串 T。T 的不平衡度为:在 S 中第 l 个和第 r 个字符之间出现的 0 和 1 的绝对差值的最大值,其中 0 <= l <= r < S 的大小。我们必须找到 T 可能的最小不平衡度。
因此,如果输入内容为 S = "0??0",那么输出将为 2
要解决这个问题,我们将遵循以下步骤 -
Define a function check(), this will take S, x, L := 0, R = x B := true for initialize i := 0, when i < size of S, update (increase i by 1), do: if S[i] is same as '0', then: decrease L and R by 1, each if S[i] is same as '1', then: increase L and R by 1, each if S[i] is same as '?', then: if L is same as R, then: B := false (decrease L by 1) (increase R by 1) if R is same as x + 1, then: if B is non-zero, then: (decrease R by 1) Otherwise R := R - 2 if L < 0, then: if B is non-zero, then: (increase L by 1) Otherwise L := L + 2 if L > R, then: return false return true From the main method, do the following L := 1, R := 1000000 while L <= R, do: Mid := floor of (L + R)/2 if check(S, Mid), then: R := Mid - 1 Otherwise L := Mid + 1 return R + 1
示例
让我们看看以下实现以获得更好的理解 -
#include <bits/stdc++.h> using namespace std; bool check(string S, int x) { int L = 0, R = x; bool B = true; for (int i = 0; i < S.size(); i++) { if (S[i] == '0') L--, R--; if (S[i] == '1') L++, R++; if (S[i] == '?') { if (L == R) B = false; L--; R++; } if (R == x + 1) { if (B) R--; else R -= 2; } if (L < 0) { if (B) L++; else L += 2; } if (L > R) return false; } return true; } int solve(string S) { int L = 1, R = 1000000; while (L <= R) { int Mid = L + R >> 1; if (check(S, Mid)) R = Mid - 1; else L = Mid + 1; } return R + 1; } int main() { string S = "0??0"; cout << solve(S) << endl; }
输入
0??0
输出
2
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