Submission #1311726

#	Time	Username	Problem	Language	Result	Execution time	Memory
1311726		samarthkulkarni	Lightning Rod (NOI18_lightningrod)	C11	Compilation error	0 ms	0 KiB

Main

#include <stdio.h>
#include <stdlib.h>

// Fast I/O for C11
// Uses getchar_unlocked (standard on Linux judges) for max speed
inline int readInt() {
    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'); // x = x * 10 + digit
        ch = getchar_unlocked();
    }
    return x;
}

// Global arrays are stored in the data segment (not stack), 
// preventing Stack Overflow for 10^7 elements.
#define MAXN 10000005
int X[MAXN], Y[MAXN];
int avl[MAXN];

// C doesn't have a built-in abs() for ints that is as fast as a macro/inline
#define ABS(x) ((x) < 0 ? -(x) : (x))

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

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

    int p = -1; // Stack pointer

    for (int i = 0; i < n; i++) {
        // Step 1: Check if building 'i' is already covered by the stack top
        // Rule: |Xi - Xj| <= Yj - Yi
        if (p >= 0) {
            int top_idx = avl[p];
            if (ABS(X[i] - X[top_idx]) <= (Y[top_idx] - Y[i])) {
                continue; 
            }
        }

        // Step 2: Check if building 'i' covers buildings already in the stack
        // Rule: |Xi - Xj| <= Yi - Yj
        while (p >= 0) {
            int top_idx = avl[p];
            if (ABS(X[i] - X[top_idx]) <= (Y[i] - Y[top_idx])) {
                p--;
            } else {
                break;
            }
        }

        // Step 3: Add current building to the stack
        avl[++p] = i;
    }

    printf("%d\n", p + 1);

    return 0;
}

Compilation message (stderr)

/usr/bin/ld: /tmp/ccyEx9cU.o: in function `main':
Main.c:(.text.startup+0x15): undefined reference to `readInt'
collect2: error: ld returned 1 exit status