제출 #1311727

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1311727		samarthkulkarni	Lightning Rod (NOI18_lightningrod)	C11	0 / 100	1 ms	340 KiB

Main

#define _GNU_SOURCE
#include <stdio.h>

// Fast I/O using the fastest available character reader
inline int read() {
    int x = 0;
    int ch = getchar_unlocked();
    while (ch < '0' || ch > '9') {
        if (ch == EOF) return -1;
        ch = getchar_unlocked();
    }
    while (ch >= '0' && ch <= '9') {
        x = (x << 3) + (x << 1) + (ch - '0');
        ch = getchar_unlocked();
    }
    return x;
}

// Global memory allocation (10^7 elements)
#define MAXN 10000005
int X[MAXN], Y[MAXN];
int avl[MAXN];

// Macro for absolute value to avoid function call overhead
#define ABS(x) ((x) < 0 ? -(x) : (x))

int main() {
    int n = read();
    if (n <= 0) {
        if (n == 0) printf("0\n");
        return 0;
    }

    for (int i = 0; i < n; i++) {
        X[i] = read();
        Y[i] = read();
    }

    int p = -1; // Stack pointer

    for (int i = 0; i < n; i++) {
        // Condition: |Xi - Xj| <= Yj - Yi
        // This is equivalent to saying Building j protects Building i
        if (p >= 0) {
            int top_idx = avl[p];
            int dx = X[i] - X[top_idx];
            if (ABS(dx) <= (Y[top_idx] - Y[i])) {
                continue; // i is already protected, skip it
            }
        }

        // Check if current building i protects buildings already in the stack
        while (p >= 0) {
            int top_idx = avl[p];
            int dx = X[i] - X[top_idx];
            if (ABS(dx) <= (Y[i] - Y[top_idx])) {
                p--; // Building in stack is now redundant
            } else {
                break;
            }
        }

        // Push current building index to stack
        avl[++p] = i;
    }

    // Output the final count of unprotected buildings
    printf("%d\n", p + 1);

    return 0;
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 7
• Subtask 3: 0 / 12
• Subtask 4: 0 / 21
• Subtask 5: 0 / 26
• Subtask 6: 0 / 10
• Subtask 7: 0 / 20