57 lines
1.4 KiB
C++
57 lines
1.4 KiB
C++
#include <string>
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#include <iostream>
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#include <cstring>
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/**
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* 1041. Robot Bounded In Circle
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* On an infinite plane, a robot initially stands at (0, 0) and faces north. The robot can receive one of three instructions:
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* "G": go straight 1 unit;
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* "L": turn 90 degrees to the left;
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* "R": turn 90 degrees to the right.
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* The robot performs the instructions given in order, and repeats them forever.
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* Return true if and only if there exists a circle in the plane such that the robot never leaves the circle.
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*/
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class Solution {
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private:
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// N, E, S, W
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inline static int dX[4] = {0, 1, 0, -1};
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inline static int dY[4] = {1, 0, -1, 0};
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public:
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static bool isRobotBounded(std::string instructions) {
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// instructions = instructions * 8;
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instructions.append(instructions);
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instructions.append(instructions);
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instructions.append(instructions);
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int l = instructions.length();
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int X = 0, Y = 0, D = 0;
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const char* const str = instructions.c_str();
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for (int i = 0; i < l; ++i) {
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switch (str[i]) {
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case 'G':
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X += dX[D];
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Y += dY[D];
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break;
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case 'L':
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D = (D + 3) % 4;
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break;
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case 'R':
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D = (D + 1) % 4;
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break;
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default:
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; // Should never reach here.
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}
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if (!X && !Y && !D && !std::strncmp(str, str + i + 1, i + 1)) {
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return true;
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}
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}
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return false;
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}
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};
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int main() {
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bool ans = Solution::isRobotBounded("GL");
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std::cout << ans;
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return 0;
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} |