Solution.ts

function minimumSubstringsInPartition(s: string): number {
    const n = s.length;
    const f: number[] = Array(n).fill(-1);
    const dfs = (i: number): number => {
        if (i >= n) {
            return 0;
        }
        if (f[i] !== -1) {
            return f[i];
        }
        const cnt: Map<number, number> = new Map();
        const freq: Map<number, number> = new Map();
        f[i] = n - i;
        for (let j = i; j < n; ++j) {
            const k = s.charCodeAt(j) - 97;
            if (freq.has(cnt.get(k)!)) {
                freq.set(cnt.get(k)!, freq.get(cnt.get(k)!)! - 1);
                if (freq.get(cnt.get(k)!) === 0) {
                    freq.delete(cnt.get(k)!);
                }
            }
            cnt.set(k, (cnt.get(k) || 0) + 1);
            freq.set(cnt.get(k)!, (freq.get(cnt.get(k)!) || 0) + 1);
            if (freq.size === 1) {
                f[i] = Math.min(f[i], 1 + dfs(j + 1));
            }
        }
        return f[i];
    };
    return dfs(0);
}