No.256 - LeetCode[457] Circular Array Loop - 模拟题

ShellDawn

于 2021-02-20 22:48:13 发布

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分类专栏： leetcode 文章标签： leetcode

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/*
 * @lc app=leetcode id=457 lang=cpp
 *
 * [457] Circular Array Loop
 */

// @lc code=start
class Solution {
public:
    bool circularArrayLoop(vector<int>& nums) {
        int N = nums.size();
        if(N < 2) return false;
        int V[N];
        int loc;
        int cnt;

        // forward
        memset(V, 0, sizeof(V));
        cnt = 0;
        for(int i=0; i<N; i++){
            if(V[i] == 0 && nums[i] > 0 ) {
                cnt++;
                loc = i;
                while( V[loc] == 0 && nums[loc] > 0 ){
                    V[loc] = cnt;
                    loc = (loc + nums[loc]) % N;
                }

                if( nums[loc] < 0 || nums[loc]%N == 0 || V[i] != V[loc] ){
                    continue;
                }

                return true;
            }
        }

        // backward
        memset(V, 0, sizeof(V));
        cnt = 0;
        for(int i=0; i<N; i++){
            if(V[i] == 0 && nums[i] < 0 ) {
                loc = i;
                cnt ++;
                while( V[loc] == 0 && nums[loc] < 0 ){
                    V[loc] = cnt;
                    loc = (loc + nums[loc] + 1000*N) % N;
                }

                if( nums[loc] > 0 || (-nums[loc])%N == 0 || V[i] != V[loc] ){
                    continue;
                }

                return true;
            }
        }
        return false;
    }
};
// @lc code=end