Loop Invariant

A loop invariant is a fact that stays meaningful before and after each iteration.

loop_invariant.c

#include <stdio.h>

int main(void) {
    int limit = ;
    int total = 0;
    int processed = 0;

    while (processed < limit) {
        processed++;
        total += processed;
    }

    printf("processed=%d\n", processed);
    printf("total=%d\n", total);
    return 0;
}

#include <stdio.h>

int main(void) {
    int limit = ;
    int total = 0;
    int processed = 0;

    while (processed < limit) {
        processed++;
        total += processed;
    }

    printf("processed=%d\n", processed);
    printf("total=%d\n", total);
    return 0;
}

#include <stdio.h>

int main(void) {
    int limit = ;
    int total = 0;
    int processed = 0;

    while (processed < limit) {
        processed++;
        total += processed;
    }

    printf("processed=%d\n", processed);
    printf("total=%d\n", total);
    return 0;
}

invariant `total` is always the sum of the values processed so far.

processed count `processed` records how many values have contributed to the invariant.